Hello Ben,
If you look at my avatar you will notice that I too have an A-Frame theater room. In my case my projector is an epson 5040ub which has lens shift etc. and it sits on the opposite end of the room. Projectors take a lot of planning even when they have lens shift. If you go for one that doesn't have it, you will need to perfectly align the projector and the screen. Without lens shift and good lens Zoom, you may not be able to place the projector so that its out of the way. Prior to buying one you should spec out the room and screen size, to make sure that the projector will work for your set up. This includes using one of the various projector calculator available on the web (usually the manufacturer of your projector will have some sort of calculator). There are plenty of Projector mounts that have extension poles to allow you to lower the projector to a proper height. The other alternative would be to table mount the projector, but this could be a problem since it may end up in your field of view. Good luck.
