Whats up Tim.
I'm using .90 styrene (High Impact) from GEPolymershapes in Mira Mesa and its pulling well on a 4.5HP vac. A 8'x4' ran about 25.00-30.00, and they will cut it down to (4) 4'x2's for free. I am curious to try .60 on some pieces, but as others have said, it could get quite thin.