Re: Can I ceiling mount a projector on a sloped ceiling?
There's a lot of ways to do what you want, and a lot of the choices depend on your carpentry abilities and the tools you have available.
One way to do it would be to make a wedge-block out of pretty much anything. It doesn't need to be solid; being "hollow" means that you can then just pop it onto the ceiling with Snap Toggles (
TOGGLER® - Products - SNAPTOGGLE®//Hollow-Wall Heavy ) and then put the "lid" on it that is your mounting plate. This could be plywood and 2x4s without any difficulty, or all sorts of other things.
If you wanted to be fancy, you could toggle on some sort of "plate" that's flat to the ceiling. Say, a 3/4 piece of MDF that has two beveled edges (longer surface away from the ceiling,) and then matching "counter-bevels" that allow you to just slide your block sideways onto the plate for removal or installation.
I'd be disinclined to use lag-bolts unless you knew you were shooting into the studs. And even then, maybe not.
And then there are "Z"-clips.. a pair of strips go on the ceiling (screw to studs,) and a pair of strips go to the block; slide into place.
A few words of advice: this isn't difficult stuff, and it doesn't need to be able to support a ton. On the other hand, you want it to be solid and not bounce, and it does need to be able to support the weight of your projector, mounting hardware, and everything else. Or, do it right, but don't over-engineer it!
Leo