DIY sump

I just bought at 20 gallon tank to redo/upgrade the 10 gallon single baffle I made some time ago. I was going to purchase a kit from http://stores.ebay.com/usa-refugium but they don’t have exactly what I was looking to build. I have a few questions as I want to make a solid sump this time. What is the best acrylic to use and thickness? Does the hydroscopic property of acrylic only matter outside of water? I seem to have no problems with the baffel in my sump, but the pieces on top of my tank warp like crazy. Any opinions on any of these designs? I’m going to have my inflow from the tank, an aqua c remora hang on, two little fishies, 200W heater, refugium, and mag5 outflow through a jbj chiller. http://www.toddah.com/Pix/Reef/sump2crop.jpg http://farm1.static.flickr.com/111/3...b4f833.jpg?v=0 http://www.ultimatereef.net/uploader...ftSumpView.jpg http://www.wetwebmedia.com/SystemPIX...ix/Sump123.jpg http://www.aquaria.info/modules/PNph...s/sum...