Been useing a Compass Circle Cutter by X-acto for the last 15 years. Good enough to cut windshiald cooling hole and cutting wheel holes. Just score the circle a couple times or till it cuts through lexan and bend the circle out, and knock out lexon. Then sand out to finish. Take your time you may not have to sand it.
Cutting cooling holes follow the track rules. Or with ROAR Rules 1/3 of windsheild or 60mm Square or circle on road. 1/2 windsheild for Off-roaders