I changed my mind, after doing more research, it seems I was correct in that melamine IS junky. It is very heavy, it sags, it swells with moisture... no thanks! It might be fine for some, but when I build something, I want to to be strong and LAST for a long time. I'm still not sure what to use yet. I'm tempted to just scrap the whole thing and buy a commercial PVC rack, but I might still do my original idea of high-grade plywood (much stronger than melamine), and seal it with acrylic paint.