Nice work! I'd been thinkin about something like that myself. everything is so crammed inside my cheap mid tower, i got a huge heatercore mounted in the top 5 1/4 bay, and an ehiem 1250 supervelcro'd to the bottom. can you say tight???
nope... go for it... i already won in a case mod show and glow.
couple tips... a sheet metal break(bender), die grinder, and good snips are the key. i used 8th inch alluminum in champayne metallic color. also i rivited it to the bought case and cut a hole for the water tubing. good luck!