They work very similar on glass as they do on acrylic...the air gap is pretty close to being the same. But, I still haven't had a chance to experiment with larger tanks yet.
So, if you have a smaller tank...here's what I can make. I have several pre-made as well. The cost covers the magnets, epoxy, plasti-dip coating, mold, shipping, etc.
Small, encrusting frags (mushrooms, GSP, etc) for glass thickness 1/8" - 1/4" = $2.50 each
Medium, encrusting frags (acans, favias, etc) for glass thickness 1/8" - 1/4" = $3.00 each
Large, small SPS frags (3" or shorter) for glass thickness 1/8" - 3/8" = $3.50 each
XLarge, medium SPS frags (4" or shorter) for glass thickness 1/8" - 3/8" = $4.00 each
XXLarge, SPS colonies (4" around) for glass thickness 1/8" - 1/4" = $4.50 each