Rule of thumb usually is this: sitting in the seat, with your helmet on, make a fist, and put it on top of your helmet. 4 fingers high, and you’re not touching the roof, you’re good. 4 fingers high, and you’re touching the roof, risky, but acceptable. Can’t do 4 fingers high, don’t use that cage. In the case of a rollover, your changes of breaking your neck, and being paralyzed is greatly affected.