well cutting you have to be exact or your screwed and silicone does only work for glass suck on acrylic. your best bet is planing the pieces that you need (sides, bottom, and all others) add up totals and call up a plastics company (near rochester laird plastics ) have them cut the pieces and most of the time they will have weldon (i recommend weldon 3 its like water ) and an applicator. weld on is on line too. heres a few great links

http://www.melevsreef.com/index.html

http://www.youtube.com/watch?v=hT6Ow_cBTps