building a perspex computer case

hi guys im building a perspex computer case, and i plan on using a tool (forget what its called) to heat the perspex, then bend it at a 90* angle 4 times so that it joins and makes a rectangle/square shaped box, then i plan on getting 2 pieces of perspex and placing them on the backs and front of the square/rectangle.
My question is... what size do you recommend that i use to build this case, and is it possible to get a plan of all the measurements to use as a draft copy so that i can get a few ideas off it, if you have any suggestions, please post i would really appreciate it, cheers