You aren't building an entire case out of plexiglass are you? That doesn't sound very wise to me. Plexiglass is ok for a window in a side panel or even an entire side panel but if you are trying to make the entire case from plexiglass you are asking for trouble. Plexiglass attracts static electricity like there is no tomorrow.
There is a good reason why most of a computer's case is made of mostly metal, it forms a sort of chasis(floating) ground. That is why everyone always says that if you don't have a wrist strap you should grab the case before messing with sensitive components inside. You discharge the static from your body to the case instead of directly to your mobo or vid card, etc...
Now if you are going to build a metal framework and use plexiglass panels that would be safer. In that case you'd probably be better off getting a generic case with removable side panels and replacing them with plexiglass panels. Less work and you still get the general effect.