I've published a 3D model of the frame I'm starting to build here thought some of you might find it interesting.

Nice work

My first remark would be: try to find a solution to your side construction because otherwise it will be a real pain to get in the car ;-)

Geoff

Previously I've built a built a full size MDF mock up of the driver 'tub' to test this and the situation will be OK.
External to the frame you see here are aluminium 'boxes' that stiffen the side frames in torsion some more.

What software did you use?

I modeled this in SolidEdge and used their web publish functionality to show it on the web.