Main Hoop
I didn't want my main hoop pushing in on my back seat so I chose this position. See the picture with the short 90.
After cutting the floor sheet metal out I found the best center line with for the main hoop and used autocad to help calculate the bends. See the autocad pics for the correct placement and bend angle for our cars. This follows the cars contour. Notice THAT THESE MEASUREMENTS ARE 6.5" CENTER LINE RADIUS, THIS IS THE SIZE DIE I USED TO BEND THE TUBING.
The picture shown here show the main hoop all the way up, this is just for new until I tack their position. The main hoop will acutally sit abut 1/2" away form the headliner so I can install padding. This will put the 21 degree angles in the same place as the body lines.
I also added a picture to give you an idea where the placement was compared to the body seams where the sill plate installs over the carpet.