I do the armpit trick with western saddles and it works like a charm. :)
I do find that the armpit thing will give me, at least, the shorter "best" western length while armpit length+1 hole is, for me, the best best length.
I dunno, what you guys are talking about, I can adjust western stirrups from the saddle...
It does take some practice but if you stick your leg over the front of the saddle, like up by the horn with your foot basically down on the horse's neck, then reach down and grab the stirrup, maneuvering around your thigh, it works pretty well. Don't try it with your leg back. I tried that, it didn't end well.