Another approach to making frames is to cut the last cut, (the only one that is a problem) using your scroll saw. I saw a video once from Japan, I think, where the guy cut all four corners with a scroll saw and did not go for a straight line. He ended up with wavy miter joints. I have not tried this (I do not make frames) but it may be worth a try. What he did was, overlap all four corners, hot glue them together, and make the wavy cut using a scroll saw.