After all the work I put into getting my bandsaw's fence perpendicular to the blade, I don't move it when I need to cut a miter. Instead, I use a 45-degree jig. I made one out of wood using my miter saw, but the little "lip" that keeps the jig from squeezing out of the clamp was screwed on and always came loose. So I welded one up!
Nothing too fancy here. Just some scrap 1" tubing I had left over from other projects, and a small piece of flat stock as the "lip". I didn't want to take a chance on warping it out of flat/true, and I needed it to lay flat, so I just tacked it up with a couple tacks on each joint and then ground them down.