As long as it's a 2" OD or larger diameter with .120" or thicker walls it should work fine for your application. If you haven't already, inspect the aluminum rivets on all the crossbar supports and replace any broken or missing ones. I would not add "more sections" not made by Rohn specifically for the purpose; these things have to taper to be structurally sound, so another base section needs to flare wider than the original one. Tilting it up with a heavy load at the top might do some damage; I'd install the tower with only the rotator and mast installed, tip it up, bolt it in place, then use a bucket truck to add the antenna(s) if at all possible. Once that large beam is installed, tilting it back down will never allow it to tilt all the way down, anyway.