Adding torsional rigidity, How do I get the front half tight? Options

[phillstek]

Once again I prevail upon the expertise here.

I have stiffened the rear of the car substantially, as shown in pics. Tubes go from rear towers through engine bay and firewall to rollbar. Rollbar is plated to longs and strapped to upper seat belt mount. There is a lateral bar (profiled to clear fan housing) in the engine bay. Car has the plates around the control arm consoles as well.

So the back end is solid but I'm not sure how to get the front section solid.

I'm thinking a bolt-in bar triangulating as far forward from rollbar to long (one each side like on some factory gt's).

Maybe a bolt-in from front towers to rollbar (through fresh air vents, which don't work anyway).

I don't want to weld in the bars as I won't be able to road register the car if I do.

I don't want to re-inforce the longs with a weld in kit.

The car seems to move around the scuttle and I have cracked a windscreen to prove it. Clearly the car twists in this area and this is what I want to stop.

Any suggestions, links and advice would be appreciated.

Thanks,

Phil