Joseph, I'm going to go nuts here 8-) (but I'm a real striding
affectionado).

Get some good quality, properly fitted striding skis asap and take a
couple of pro. lessons as you prep for the Norske Birkie. It sounds
like you're fit and athletic and really enjoy xc skiing in general. I
think it will make a HUGE difference for a person like you, very, very
quickly. It will not only pay off in that you will have 100X more fun
on the Norske Birke, but for years to come. Regardless of your
competative goals, you will have a night and day difference in fun.

As for the effect of your inferior, ill-fitted skis: I don't think I'm
exaggerating too much to say its like the difference between a poorly
maintained, (e.g. shifts and rolls poorly) , poorly fitted, clunky
Huffy bike compared to a good quality, well fitted racing bike. Then
you could take another step from "good quality and well fitted" to
"excellent quality and perfectly fitted" - a better and definitely
noticable improvement in both biking and skiing. But that first step
is huge, further steps are more subtle and of course expensive (but
even for duffers like me, often worth it simply because its more fun).

Sure you can have fun (sort of) on both the Huffy-grade vs. the better
quality gear. Sure you can use both for fitness. But the difference in
pleasure and effectiveness is huge.

Here's my editorial comment: and athletic person like you will come to
absolutely love striding when you get decent gear and technique, maybe
even more than skating..