I agree these things are pretty complex. What did you use for the light trap? How thin is the garolite you've used? I'm building a wetplate holder and would appreciate any tips on these materials. I decide to use 1/16" garolite since I only need one holder for wetplate and decided it could be fairly robust as a result.
I purchased a new walnut 11x14 holder from AWB several years ago and just marvel at the construction ever time I use it. Pricey, but a beautiful piece of woodworking.