dave,
couple suggestions if you don't mind
1. edging material, i'll be looking this weekend form somethign suitable, maybe autopmotive door trim? i used this last weekend and screws rolled right off and onto the floor.
2. additional cork shims/spacers on the back.
3. acorn nuts for the screws. this would help protect the finish of whatever surface it sits on as well as keep the bottom sheet of acrylic from backing out on the screw. this would require thicker shims/spacers on the back to accomodate the increased hieght. maybe reverse the screws and have the bottom almost flush with acorn nuts on the top?
4. removeable/disposable screen protectors to protect the acrylic finish on the top surface. these are too nice to scratch up