My first BUD had a plumb adjustment built in. I don't know why they don't sell mounts like this anymore, as at least an accessory. But the way the plumb adjustment worked, was that the bottom of the actual mount was connected to a flat triangular plate with an indentation in the center, and holes for bolts at the three ends of the triangle. The part of the mount that slipped over the pipe in the ground was a bigger pipe with a similar triangular plate welded to the top, again with an indentation in the center. Then they had a big ball bearing, maybe 1/2", that sat in that indentation, and the triangular plate of the upper part of the mount then sat on top of the triangular plate of the lower part with the ball bearing sandwiched between, so that the upper part could move around at any angle on top of that big ball bearing. Then, with nuts/bolts through the 3 holes of the 2 triangular plates, you could adjust the plumb of your actual mount by tightening/loosening the 3 bolts. The thing came with a little level permanently attached to the top plate, so that you could see the level as you adjusted the 3 bolts. Pretty nifty. That being said, it's not really necessary to have a plumb pole, but it sure makes things easier.