Hi Sew Please,
Yep, you can use anything as a shim (and trust me, I have). On the Accucut craft side, they make and sell a shim for sizzix dies:
http://www.accucutcraft.com/cutting-...y-adapter.html
On the accucquilt side, they make an adaptor for the GO! dies:
http://www.accuquilt.com/studio-shop...o-10-x-24.html
and yes, the Sizzix and GO! dies are different thicknesses so you need 2 different adaptors, purchased or home made.
A good quality magazine will work, you just keep testing the die (don't force it through) and keep tearing off pages until it works. Remember, you don't need the die to be embedded and inch into the cutting plastic. Keep reducing the number of pages until it just cuts.
BTW, cutting plastic is a consumable. To extend it's life, try to not make repeated cuts in the exact same area. Flip the mat end for end, use both sides, move it from side to side etc. When your cuts start leaving lots of threads, your die isn't dull, you need a new pad.
Be sure and sign up for emails from accucut along with accuquilt. Accucut has much better sales and many of the shapes can be used for applique.