On the seat "Challenge", this bar is fixed between the "jaws" of the G27 and the chuck. And as soon as the unit is securely tightened, the gear lever is then in handy - and not moving. This is what I expected and I am satisfied.
Also on the "Challenge", it should be noted that this bar can interfere when folding the seat. The best solution is to loosen the bar and store it near the headquarters. This is not necessarily very nice because there is always a cable between the steering wheel (tightly screwed to its support) and the gear lever, but it's still the best compromise for optimal storage and implementation Quick.