4 or 6 point roll bar

Double-check the rules for the ET you'll be running to insure it will be legal. Without looking it up, I would doubt that a 4 pt would be legal. If you go to a 6, you might as well go 8 pt. and tie the 2 extra inboard bars into frame connectors, from the main hoop. Frame connectors are a VERY good idea, with roll bar or without.