lifting toes/wax pocket

Hi,

First season taking waxable classic skiing seriously, so my learning curve
is currently steep.

My skis are professionally fit and the grip zone marked. I find that I get
better glide, especially double poling, when I lift my toes (or press my
heels). If I press my toes down, I hit the brakes. Is this normal, or does
my grip zone extend too far forward?

To do this heel press (or toe lift), it seems to change my downhill tuck
position from the one I use skating. The classic position seems to position
me further back with straighter ankles.

If this is normal, do you try to incorporate this heel glide into each
diagonal stride, as well? Is this why the new Solomon striding boots use
the carbon heel cup?

Thanks,

Brian