To get it all in there i would situate the hoop at the 'B' pillar - forward of where you sit. I would run the rear bars back and bend down to intersect with the seat back bar which would run from each leg of the main hoop and run rearward bending around behind the seats. Additional support would then drop from the seat back bar (align with the bars from the top) and drop down thru the floor to structural members of the suspension. The main hoop bars will also pass thru the floor to connect to the frame.
If i could figure how to do an autocad dwg here i would post one up. If you don't understand then shoot me an email to ojh4@verizon.net and i'll send you a drawing.