I finally figured it out. This roll bar is for a hardtop car. The rear supports land on the tops of the wheel wells. But that is exactly where the convertible top mechanism is. What to do? I had a brainstorm, unbolted the flanges, and reversed the rear supports from side to side. I pulled the ends closer together with a come-along. Now they land just next to the top mechanism on the edge of the wells. The plate on the ends hangs over past the wells on the inside. Two bolts will be on the top of the wells. If I bend half of the plate down 90° the other two bolts will attach on the vertical sides of the wells. That is probably stronger than just the tops of the wells. I can move the top up and down without interfering with the bar. Then I found out that the bottom support plates of the main uprights land not on the rockers, but on the corners of the foot wells. I had to spread the posts with a bottle jack so the mounting plates landed tighter to the corners. They are bent to comply with the shape of the wells where they meet the rear seat support area. That is not a very strong area so I am going to fabricate some reinforcements from some 3/16" diamond plate I have. I will cut it to cover the foot wells along the rockers, and extend up over the front and rear seat support areas a few inches. That should be strong enough to support the weight of the overturned car. This is a bolt-in roll bar. It is very tempting to weld this in permanently. But I am sure it will need to be removed at some point for various reasons. Right now the entire roll bar can be removed intact by just unbolting it. Of course grade 8 bolts will be needed for strength. Stay tuned for pics.