Greetings my friend!
I am sorry I cannot read the descriptions on your web page, but I can understand some of it.
That is quite a project! I was wondering, what are your plans for the car? Will you be racing on paved sports car tracks (Touring Car -type racing?) or is it for off-road or dirt racing? (Rally type?)
In any case, I do not mean to be critical but simply to offer suggestions:
For construction of race car chassis that I have seen, the builders start with approximately 4X8 inch (100mmX200mm) steel anchor pads welded to the floors. The main pipes of the cage then are welded to these strong mounting points. I am only saying this so that you do not spend a great deal of time building a cage which is only connected to the seat belt mountings- if the car must be inspected before you race, the track officials may not approve a cage built the way you are doing it.

I wish you the best of luck and I look forward to more pictures of the project as you complete it!
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Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '84 242DL/AW70-100K, '89 244DL/AW70- 212K and I miss my: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K