Really? What blade would you use - how many teeth?
My chopsaw is using a 24t blade that I primarily use to trim up 2x4's. I'm assuming you'd want smaller + more teeth to do that kind of finishing work?
All the same, plexi costs too much to put under that if you ask me. 1/8 inch ain't worth the potential disaster. I'd go the sand paper+hand sand route.
I use a 10" 80 tooth thin kerf blade. I've cut quite a bit of stuff besides wood with my saw such as aluminum, Lexan, UHMW, PVC, etc. It is risky
cutting acrylics and polycarbonate because the piece can shatter if they are not clamped and cut properly. However,
trimming is fast, easy and gives excellent results. My
cab has more pieces of Lexan than most. Most of it was cut slightly larger than necessary with a box cutter and then trimmed with the sliding chop saw.