If my horses measure out in the range where two sizes
overlap, I buy the smaller size. With the old boots this practice made them
hard to get on and off, but I never lost one, even in deep mud. The newer
boots are easier to put on and off, but I did make the same modification to an
older pair that I had by cutting them on the front, to match the new style. My
gelding measures out at a 2, but I use 1s on him, and they are perfect and I
have not lost one yet. I haven't tried the gaiters yet, but that would help
them stay on as well. Good luck.