Hi Button, having played around with the suspension on my +8, and lowering the car I came to the following conclusions.
1 the chassis flexes a lot and this will be even more with the additional weight off the v8
2 the greater Bhp out the rear causes a lot of rear axle wind up and unsettles the car and can twist the chassis ( why people fit torsion bars)
3 the basic set up IMO is inadequate for the above
Firstly I doubt your glued tub will make much difference, wood bends. The issue I found is that as you get control of the beast with better shock absorbers, springs and set up then the trade off is a stiffer ride. A much lighter +4 is more tolerant effectively due to lower moving mass to affect the chassis and suspension do a better and more tolerant ride is easier to achieve. So IMO you may be chasing the proverbial Holy Grail, it's what is is!
Good luck
