There really isn't a spec on body. Roll bars rules they have say has to be the same width as frame or more not less has to be 4 inchs past your helmet. Up to me I would not run one why on my mower builds I take them off for other races with out local club. they won't let ous run seat belts I flip my super mod last year at the fastest gokart track and knock me out for couple mins was my own falt when spun out didn't stay in the gas so it put me in a reverse rocket to the tires
If I build a new one going to be like my new singles with a body on it
So they allowed the roll bar but did not allow seat belts?