The Peerless mount that you are using and recommend unfortunately makes it difficult to do a flush ceiling installation unless I am missing something. I would like to keep the pj as close to the ceiling as possible for aesthetic purposes so I don't want any type of pole protruding from the ceiling. Having said that maybe to get even a little vertical adjustment is going to be difficult. What do you think?
Yes, if you don't want to see the mount especially the long slide channel, that is an issue. You can do two things.
1. Do what I did, I actually cut a square hole in the drywall in my ceiling so I could mount the projector on the floor boards inside the ceiling. The projector hangs just below the hole covering most of it, so it looks like it's flush with the ceiling. I have some nice black rubber molding for the edges of the of the cut drywall which match my recessed lighting. I have to say it wasn't easy doing it this way, there's little room to work when you actually get the projector where you want it....sliding, adjusting, tightening pitch and roll, you have to take the projector off, adjust, put it back on, rinse and repeat until you have it perfect.
Now my setup is in a finished basement and like I said my ceilings are drywall with recessed lighting with a good 9 inches between the floor joists and the drywall, so I knew this would work for me.
If you look at my pic above you can see my projector at the top of the pic, it looks like it's flush mounted, but it's not....there's actually a square hole there, but you can't really see it because it covers most of the whole. You can also see one of my recessed lights to left and down a little bit.
That might not be an option for you, so if it isn't...
2. Just mount it using a low profile mount like ack_bk recommended (although not that one, no offense ack_bk), you'll just have to put the screen where the image projects a perfect rectangle. Wherever you mount it, it will project the perfect rectangle when the lens is plumb with the screen, you just won't have much control over where that is. So, you need to trust the throw calculator and if you can, with whatever mount you get, try and get the measurements of the mount and how much it adds to the equation. So if the mount adds 6 inches from ceiling to projector, take that into account.
I would look at something like this or similar: https://www.peerless-av.com/en-us/professional/products/PRGS-UNV
Thanks for all your help! I think my plan is going to be to buy it from Amazon and then play around with positioning before I mount anything permanently. I will assemble a panel of "experts" to decide what image size they like the best and then go from there. The room hasn't been drywalled yet so I can put the mount and ceiling outlet anywhere I want. I think a ladder, an extension cord and a bedsheet should get me where I need to be.
That's the way to do it, and with a new room you can really nail it.