Rollbar mounting for M38A1

Hey there all,

I just picked up a roll bar for my 1953 M38A1 since the military Jeeps didn't have them. Before cutting and welding anything, is there a specific measurement that the upright should sit behind the driver's seat? This is a 4-point rollbar and there seems to be about 8 inches of fore and aft "play room" for me to mount it. should the rollbar be as far back as possible or as far forward? Any help would be appreciated.

BTW, I will be bolting the bar to frame supports through the rear wheel wells, so "measure twice, cut once" is the goal here. Any other things I need to consider? Thanks! -Rob