I took a few runs once on my brother's identical setup -- heavy, but
impressive!

Anyway, ignore the boot size (i.e., 26.0/26.5) and instead go by the
boot sole length (i.e., 30.5cm/305mm).

You might want to skip all the other alignment methods and just match
up the ball of your foot with the middle of the ski’s contact
length - hard to measure, but it’s what every other technique is
trying to simulate.

Here are some other Diamir mounting tips I copied from someone else's
post a few yrs ago -- I can't vouch for how well they work, but they
certainly seem well thought out:

*****

Regarding mounting the bindings, the real challenge is getting the
template located correctly fore & aft and making sure it's accurately
centered on the ski. The real risk is if the bindings end up slightly
angled on the long axis of the ski. Not an easy problem to solve.

Here's what I've learned from mounting about six pair of these.
1. Locating binding fore & aft: Measure your boot to determine the
sole length in mm's. The sole length should be stamped on the side of
the boot. My boots, for example, have a 299mm sole length. On the
template, there are a series of boot sole lengths marked off in cms.
Find the length that most closely corresponds to your sole length (in
my case a 299 mm boot sole would be located just short of the 30 cm
line) and match that up with the boot sole midpoint line on your skis.
This gives you the correct fore & aft location. If your skis don't
have a midsole mark, you can mount using the toe of the boot method.
Let me know if that's the case, and I'll give you the details for that
if you don't know them already.

2. Locating binding on the long axis: Getting the binding accurately
centered is critical. There are centering lines on both ends of the
template. Measure the width of the ski in the area where the centering
lines will be located and mark the center point on the ski with a
pencil. Accurately measuring the center point can be hard on cap skis.
It's easier if the skis have vertical sidewalls. Take your time in
measuring for the center point and check your work a couple of times
to make sure you're right on center. The template also has a series of
lines along the edges on both ends that will also help you get it
centered. Do not trust the graphics of the ski as reference points.
Often times the graphics are not perfectly centered on the top of the
ski. I find that if I get one end located and centered, I can then
slowly bring the other end of the template down and center it. Don't
be afraid to pull the template up multiple times if you're not right
on the marks. It has enough stickum to be used several times. An extra
set of eyes to look at the template once you think you've got it in
the right spot are helpful because you can get a bit cross-eyed
looking at it.

3. Punch: Once you're confident that you've got the template in the
right spot and have checked and rechecked your measurements for & aft
and side to side, take a punch, put it in the crosshairs of the
circles on the template and give it a good whack with a hammer. Make
sure you hit the right holes on the heel piece. The dark circles are
for the medium length binding. Use the spots marked S or XL only if
you've got a small or XL binding. There are four holes for the toe
piece and three for the heel piece.

4. Drill: Ideally you'll have a 4.1 mm x 9 mm bit with a stop on it to
drill the holes. If you don't, figure out what the English equivalent
of a 4.1 mm bit is. I think its a 5/32" but you'll have to do some
higher math or check in a hardware store to make sure you've got the
right sized bit. If you end up using a drill without a stop, wrap some
tape around the shaft of the drill at the proper depth so that you
don't have the thrill of drilling right through the ski. Use a sharp
bit because it won't tend to "run" sideways when you drill. If your
drill doesn't have a stop, you should very lightly countersink the
holes. Don't remove too much of the top sheet of plastic, but a little
bit of countersink keeps the holes from turning into little volcano
shaped things that keep the binding from laying flat on the ski. I
think it's best to drill and mount one ski at a time. That way if you
screw up on the first one, you won't have already drilled and made the
same mistake on the second one. You can punch both of them at the same
time, but wait to drill the second one until the first one is mounted.

5. Screw: Mount the heel piece first and tighten the screws down. I
put a drop of Elmer's white glue in the holes before I screw them
down. I thinks there's a thin, clear plastic spacer that goes under
the heel piece. The printed directions are pretty good for this part.
Once the heel unit is mounted, screw in the toe piece. There's a
plastic piece that goes between the binding and the ski. Do the front
screws first and don't tighten them all the way down. Flip the rail up
perpendicular and screw in the remaining two screws, but don't snug
them up. Bring the rail down and make sure that it drops squarely into
the opening in the heel piece. If it's a little off center you can
give the whole thing a bit of a twist to line it up and then crank the
screws down to hold it in the right spot. Make sure that the binding
is snugged down flat on the ski. If the rail rubs a little bit on one
side, its not a big deal. The main thing is to check to make sure that
the whole unit is on straight and not aiming off into left field or
right field. If you did your measuring right, there's no problem. Once
you do one ski and get it right, then repeat the process for the
second ski.

6. Adjusting: Cock the heel piece and put the boot in the binding.
Flip the climbing aid up to its highest position (with the boot in the
binding) and turn the screw at the rear end of the center rail to
adjust for length. The heel piece has to be in the closed position for
this to work right. When the head of the screw is flush with the
plastic housing, you've got the correct amount of forward pressure.
Put the boot in and out of the binding a few times and recheck to make
sure that the screw is flush. Adjust it if it's not. Adjust the toe
height by turning the screw on the top of the toe piece. You want to
have about 1mm of space between the boot sole and the skid plate. I've
got a thin piece of plastic about the thickness of a credit card that
I use as a feeler guage to check this. Check to see that toe of the
boot recenters itself when you give it a firm push from the side. If
it doesn't, you've either go too much down pressure or too much
forward pressure or both. Back off the forward pressure a bit and if
the boot still hangs up, then back off on the toe piece height
adjustment screw. Fiddle with these two until you get the boot
securely in the binding, but able to recenter.

7. Release settings: The forward release is controlled by a screw on
the top of the heel unit. There's a window on the heel piece that has
the DIN release values marked The lateral release is adjusted by a
screw on the front of the toe unit. There's a window on the center
rail that has the DIN release values for the toe piece. The release
settings are up to you. If you can find a shop that works on these,
they could check them for you. Most shops won't touch them. There's a
chart on the directions that has the release values.

8. Brakes & crampons: If you use them, the brakes screw onto the heel
piece. There's a plastic heel plate that you flip out with a
screwdriver and the brakes screw into the holes underneath with the
two screws provided. I recommend brakes over straps particularly when
things start to slide. The crampons have little ears on the front that
slip into slots in the toe piece and then they clamp down onto the
center rail. Most of the time you carry them around wondering why you
bother with them, but when you need them, you wouldn't want to be
without them.

9. Go skiing: