[Ant]

Hi Steve

My tunnel is glass with no tubing, the ladder has a good x brace through to the gearbox x member and then its just two big hunks of 4X3 RHS going through to the front suspension the rhs kicks up after the engine mounts and has gussets in this area.

I think a backbone would help the central part of the chassis, the rear and front of the car is well designed and well braced!
Mounting the engine and transmission solid and making them part of the chassis would strengthen the center to within a few inches of the front suspension, but I dont know whether thats such a good idea.
My last Cobra has the motor solid with rod ends etc, maybe some hard bushes with a small amount of compliance may work better depending on design!

Ant