Check with your local Frame Shop, find out if they have a chopper, and have them miter them on the chopper. (not to be confused with a miter saw) these use knives instead of rotating blades, a much nicer edge, particularly on finished stock
Don't really need but one "stop" since you _always_ make the cuts in a particular sequence if you want to take advantage of the built-in complementary angle and length precision.
Having only one stop allows the two oppopsing sides to be precision cut to length (as well as keeping you from cutting out of sequence).
For a "stop" on the left, simply cut from "right to left".
IOW, on each piece make your first miter cut to the right of the blade and make your second miter cut, for length, to the left of the blade.
Obviously, always cut the two pieces that need to be the same length before moving the stop.
Easy/elegant/dummy proof ... and I need all of the latter I can get.
One thing I forgot to mention that it is so obvious that only a dummy could miss it, but always make your cuts with the same face up. Of course, neither you nor I would ever fail to do that, would we?
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