Thanks Chad, I threw out 20 feet because that is the distance from the rear wall to where the screen will be and would be the easiest place to put the projector. I hadn't done any research at that point and now see that is too far. It looks like a ceiling mount is the only option. I've also done a bunch of googling on DIY screens and that looks very doable. I'll look into the 720P models.
Thanks to everyone so far.
Thanks to everyone so far.