on the main hoop, the big part from rocker to roof- across the car and back to rocker, the supporting bar where a "seat belt" would install directly behind the driver going across the main hoop- what size does this need to be, i bought a chis alston kit for my barracuda and it came with a few extra bars... do i need to use the 1 3/4 or the smaller tube for this? I have enough to do either