It is probably safer to add raising to your footwear than to try to put
blocks on the rudder pedals. I have raising on my right boot, as my
right leg is several inches shorter than the left, as part of my
standard equipment for walking, anyway. Surgical footwear, for want of
a better description, is designed for the job. A do-it-yourself
approach may be hard to engineer satisfactorily without risk of the
raising coming loose and causing problems, but with ingenuity it could
no doubt be done.

Modifying the glider would no doubt involve somebody having to approve
the modification and signing it off, and depending on the range of
movement, may make it difficult for other people, if you share it.

Chris N.