If you just need a really nice solid mount with a pole that you can get at any length, then try a Chief RPA series mount.
They use standard 1.5" STEEL plumbing tubing that you can pick up from Home Depot in about any length you need. I needed a 5' piece and Home Depot had it for me in 10 minutes, cut it and put threads on it right in the store.
It is not 'adjustable' in height - as I don't want the projector to move after it is mounted. But, I could have had the pole cut at any length - it was 10 feet long when I purchased it.