If your projector is attached to the ceiling joists there is not a lot you can do in my opinion. I have a DIY mount using cast iron steel attached across the ceiling floor joists in my basement. I get the occasional shaking from my subs, as well as when the kids are jumping upstairs. Provides a realism to action movies. \:\)

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85