Roll Cage design

[PoorMans180SX]

My car is in need of a roll cage. This will not be a street driven car and you can assume that whoever is riding in it will be wearing a helmet at all times. I'm talking a serious time attack/some drift cage, not just your basic 6-point.

Forgive my poor MS paint skills, but I've come up with several designs that I find intriguing, but I was hoping I could get some advice on the REAL importance of certain bars and their stiffening properties.

I know I could design some crazy monkey-bar setup, but I do want it to be somewhat lightweight. This cage will be made from Chromoly. If you want to give some advice on size and whatnot that will be cool, but I think I will ultimately let the shop decide (If I can find a good enough one)

This was the setup I was decided on for a long time (until I discovered some others). The downbars you see underneath the middle harness bar connect to the transmission tunnel.


I've noticed a lot of crossbars lately:


I'm starting to like this setup more and more for it's lightness and stiffness (the strut bar would do double duty as a harness bar):


I'm thinking this is probably the stiffest setup I can come up with without going crazy. I've also added a traingulated strut bar in, which I haven't seen on many S-chassis, but I have recently on several professional race cars, input?:


This is the classic setup I see in pretty much every full-cage drift S-chassis:


I got this design from a setup I saw in a S13 coupe:


And something similar to this from a Fastback shell on here (olive green, carbon doors? I've got photos) Obviously you could tie this into the C-pillars:


by the way the front downbars are to comply with some of the latest regulations and would pass through the strut towers completely. Any advice is appreciated. Like I said, they are just MS paint drawings, so feel free to edit and repost as you like. Thanks.