I hereby un-recommend the platen as posted here -- the acrylic flexes too much to be good. Also, the method of attaching the platen to the drawer slides is not quite strong enough. Corner braces would be better. I will illustrate with a pic, hopefully tomorrow or the next day.
That was my thought the first time I looked over this design, the 1/8" extruded acrylic (FF) is too thin. 1/4" would probably be a better choice, and even then the 90Â° joint between them ideally should be glued to get some level of rigidity.
I'm about 1/2 done with building my version of this stand and I'm mostly doing it as you have designed.
The platen I'm using was built first with the idea that it would be one of the more important parts. It's overbuilt and will be moved to the next stand when I've learned what I need to know from this iteration of the "New Standard Scanner" design.
It has been fabricated from 3/8" GP cast acrylic (Chemcast, though Cyro would be better). All joints were pin glued, routed, wet sanded and then polished with red and then white jewellers rouge.
I have some experience with acrylic and I'd like to add my 2 cents in on a couple of things.
1. When cleaning acrylic sheeting use a mild soap, do not use Windex, 409, denatured alcohol or any harsh cleaners. This not only will mar the surface but may also cause crazing of the plastic, especially if it's used on flame polished edges.
http://media.photobucket.com/image/acry ... C_1548.jpg
Ideally, use Brillianize by Kleenmaster http://www.brillianize.com/
2. Drilling is very touchy if you're in too much of a rush and using standard wood or sheet metal drills (point angle of 118Â°). If one needs to drill acrylic panels either get the right drill with a 60Â° point angle, or lubricate it with soap, fully support the stock and GO SLOW.