Installing X-Pole X-Pert in Garage - Ceiling issue?

Hi all, I have been trying to get my pole set up in the garage and we have the appropriate spots (joists, batons, etc.) measured and marked out, however when we finally got it up my partner was concerned that there was too much movement in the plaster on the ceiling. As we are renting, we don't want to risk doing too much damage to the ceiling. We are going to put a piece of MDF between the upper dome and the ceiling to help spread the pressure a bit further, but aren't sure on the best way to go about it. It would be awesome if someone out there has had the same issue and could give some tips :) Thanks heaps!