Have you tried ditching the rear anti roll bar altogether. I have had a lot of trouble getting my old Camaro handling properly since I joined a race series that required me to raise the suspension to give 4" ground clearance. I was suffering with serious terminal understeer and in an effort to cure it went up to a 1 1/8" rear anti roll bar to try to get some oversteer induced. Bad move as I went too far and terminal oversteer was the result, the car was almost dangerous culminating in a crash in wet conditions on the qually warm up lap when I gave it a tad of throttle and it just snapped around something it also done before in front of the whole field at the start but I was lucky that time, not the last time though.
So I did some serious rethinking on the front suspension as I had been up and down through the tyre pressures and it made little difference infact just changed where in the race the car peaked, i.e. low presures better at the end of the race high perssures better at the start! I worked to get the angles better through the suspension curve on the front you can even see the difference from track side photos with the car cornering hard, I then threw away the big anti roll bar at the back and stuck a thin little thing from a standard road car and I have say the difference at Lydden last Saturday was absolutely phenomenal. The back will step out with a bit of throttle (I like that) but it is completely controllable, if it starts going too far just get out the gas and she will straighten up, a real joy to drive now.
BTW is the Bristol engine you are using the BMW derived unit that went into the AC Ace? If so I completely rebuilt one of those once when I was working at Roger Nathans, fantasic old design as I recollect with hemi heads and cross over pushrods.
BTW below is a shot of the car stranded at the chicane at Thruxton as a result of the oversteer situation. :-(
