OK Cracker, I'll bite......
Unlike your present roll bar, which is probably 3" lower than the top of your head, I would recommend it be at a minimum 3" taller than the top of your melon
For those of us in the range of 6'2" and above, I would think you want the roll-bar to be "functional"
I know, this is not what you wanted to hear, but I could not resist......
Your neighbor and friend;
BigEasy