BB, what you can do to get the cut straight is to not clamp it up tight, just so you can rotate it, hold down on it cut in about a third of the way and rotate it slowly. Just be careful and take it slowly. You can also clamp it, cut in a third, unclamp it rotate, cut and repeat. You can also, if the cut is off square, lock the blade down and with the saw running push the tube up against the blade and rotate slowly and you will be able to see once it has squared up. Be aware that this will shorten the length so if you do this make sure the original cut gives you enough length to grind back
