Dennis
Bird cage timing is bird cage timing, drivers weight should not affect that part of the equation. Adjust your car with ride height. Block it as you are told 3" on left tube and 4" on right tube. Get a 150 to 175 pound driver to set in seat, measure ride height (frame to level ground both sides below axle. Install the real driver and either crank the bars up to get same ride height or install larger bars (best solution) until you get same ride height, then your bird cages will also be in time if you adjusted them at original ride height.
Back in my young days when I enjoyed working on race cars we used to change rear bars at least twice a night. Keeping the blocks the same and going smaller on bars as the race track slicked off, now we might maybe turn a few screws.
Honest Dad himself
