[Bill Wilkinson]

Sometimes it is wise to 'sister' the joists and add cross bracing in the area where the projector is going to be mounted as the room is being constructed. This will stiffen the floor/ceiling assembly and reduce the vibration from a structural standpoint.

The trouble with trying to mount the projector with vibration damping mounts is that they are so light. There are very few materials that will function properly on those light loads. You could in fact make it worse as you could increase the amplitude of the vibration with the wrong pad.
Bill

 

[Bill Wilkinson]

I should have been clearer. Ted you are right you can't do just a small area it would have to be sistered back to 'room edge support point' to be effective.
I love isolators and use them all the time but using the wrong one could leave you in a worst off condition actually increasing the amplitude. Perhaps as you have suggested using 4 mounts on two pieces of furring channel with a broad base of double layered plywood, Green Glue between the layers for damping. Screw the plywood assembly to the furring channel and the projector to the plywood base. Paint it to match the room. Does any company make a kit for this?
Bill

 

[Bill Wilkinson]

I think it would do a fine job. The only challenge would be to make it look nice enough to get the "wife approval". The clip and furring channel would keep the dampened wood 'base' off the ceiling by approx. 1-5/8" so if you put edge return molding on this to go back to within say 3/8" of the ceiling, leaving a reveal, it would look like it was cabinet work put in place to mount the projector.
Bill

 

[Bill Wilkinson]

I'd want to be doing it while I was using Green Glue for something else. I would not want to waste a whole tube.
Question: Is this just an annoyance as someone walks over making the projector shake or can it actually damage some/all projects over time?
Bill