The percentage of static weight on the rear wheels should be no more than:
(L-2.5H)/L
where "L" is the wheelbase and "H" is the center of gravity height. The "2.5" is the coefficient of friction for a good set of slicks. The static weight bias should be determined with the driver in the car, of course. It would appear that you'll need to shift some weight to avoid unloading the rear tires with excessive wheelie bar loads.
With no suspension, it is important to build some "droop" into the left front in order to keep the rear tires equally loaded on launch (and, it should be stressed, to maintain some degree of driving safety). To determine the amount and its effectiveness, you'll need to use a traction dyno. (See Pages 4, 5, and 6 below.)
Hope this helps.