Guys, just a thought. If you roll that, with one inch of clearance between your helmet and the bar, you are going to compress someone's spine…
Add the seat, and run a string from the top of the rollbar to the highest point on the front of the chassis, with Ike sitting in the seat. If the string contacts his helmet, the rollbar is too low, and needs to be taller. If not, and the thing turns turtle, someone's gonna get hurt – badly.
A third tube, at the apex of the rollbar like a dragster will provide three-point structural strength, and keep the rollbar from bending over, in case you take a digger. Be safe, and plan for the worst…
P.S. – a little padding on those rollbar downtubes will also keep you from getting your bell rung, if there is violent side-to-side motion…