If you're fitting them yourselves (or at a garage) remember the wheels should be supporting the weight of the car and not any ramps, axles stands etc.
If you don't do this, once you've fitted the bar the rubbers, etc will twist as the wiegh goes back on. Basically you'll be clamping it in a position that's not it's normal resting place.
This is why the Audi instructions make it clear not to do it with the wheels hanging.
Being old-fashioned, I think of ramps as being the wedge shaped metal frameworks that cause teh wheels to continue to support the weight of the vehicle, but approx 10" above the ground.
And the original hydraulic ramps are moving "wheel tracks" that can be raise many feet into the air.
Can you not use either of these to install the RARB, or will I *have* to get the car on the ground to bounce the suspension to settle the mounts before completing the clamp tightening?
A hoist, however, may allow the wheel to be hanging free, as is needed for many servicing operations (but not this one)
Obviously, if you let the wheels hang down, then the shape of the ARB is extended slightly (end to end), and so cannot be fitted without excessive force.
I'm surprised about the comment about the bush sizes; too much sticking and there will be residual lean, but too slack, and the roll-resistance will be decreased. So fitting the "A" bushes to the 22mm ARB might be slightly sticky, and will be worst when initially fitted, and will only wear into a "better" more nominal state. Of course, fitting the right "D" bushes to the 22mm ARB will have the right level of "give" to reduce vibration, etc.