Chazz, I can't see any reasonable way to attach it to those body mount points. Not without turning the whole thing into a giant steel mousetrap. Also, I'd hate to bridge the body-frame gap and bring in NVH issues.
When I first built it, I only had the 4x4" floor plates and 3 bolts. That was really bad. I think my 5 year old son could have pushed the hoop forward and twisted the floor upwards. Weakest floor I have ever seen. That's why I added the doubler plates, 6x12, with 5x10 backers on the bottomside. Not the hoop rings like a bell. The backstays are gravy. On the final install, I'll also shoot a bolt sideways through the wheelwell.
I have thought about running another tie-point to that mount just below the Alpine light... but sometimes you have to say enough is enough.
I've heard that about the roof, that they're solid on these trucks. The main thing is that the hoop doesn't collapse in any way, and hopefully I've accomplished that.