I found some pipe insulation lying around, split it in half, and cut notches at the appropriate intervals.
(I used 2 strips, on top edge.)
Works great, cheap, and only tool required is a pair of scissors!
c32
Oh, and going back to physically stabilizing the cards, did anyone else think to use the mount-holes on the H-cards to bind them together using bolts, dowels, or something similar? I imagine it would be quite tedious to set up and you would want to make sure the cards where working well first...