[Milsurplus] Cutting Thick, Clear Plastic

[David Stinson]

Thanks for writing, ya'll.
I should have been clearer.
The plastic is about 1.5 times as thick as a computer CD disc,
and about the same flexibility; perhaps a bit more.
Isn't Lexan much thicker?  
My hand isn't nearly steady enough to cut a circle cleanly
with a Dremel tool free-hand.  (Light-bulb just went on)-
Would this work: fix an arm or "jig" to the center of the circle
being cut, using it to hold the Dremel tool at the right diameter as 
I rotate it all the way around.  My concern: even on low speed,
wouldn't a Dremel get too hot for such thin plastic?
And if so, what would work?  Should I just use a scribe and 
be patient?
Thanks again,
D.S.