at 55 mph it takes 7/10s of a second to have your front rib area to touch the spine..Think about that when you have a funny car cage...

If you dont run the car hard most of the time then shy away from the extra cage...Om a street car i always recommend that my customer really thinks about not running a swing out bar...It makes the cage weaker.This is during a crash and during a pass..

If you plan on a cgae or bar then forget the back seat..As siad above its pretty dangerous in a wreck..

Have the door bars contoured lower so you can climb over them..I usually brace these to the sill running toward the main hoop also..

As for the X bar on the main hoop you cant make it removeable but i have gotten away with countouring it further back so the seats recline a little..

Now ive also built a car or two with the fc cage on a dual purpose car..I used some alloy plate and some high density foam about 2" thick...I dont know if this would help but i hope it does if the guy ever wrecks..