Hi, Alex you are right about having mass moving forward. With (let me rephrase, thanks Sammies too!) up travel available on the rear axle, when you go off throttle, while the rear rises, but it will not be stopped by the droop's grub screw, rather it will allow the chassis to rise but not trying to lift the wheels off the ground. This will allow the rear wheels to maintain that little more traction.
To start off, what I suggested, it will most probably make the rear pretty planted, but the steering will be kinda blunt. Gradually reduce rear up travel with a quarter turn at a time. Its very interesting to try this. I've always found it very effective.
Cheers!!