Mexican carry seems to work OK with longer guns and/or semi-auto's, but when I tried with my 2" j-frames I discovered they didn't want to fall down into my britches but had a tendency to want to pop out of my waistband-- not a good thing. BTW this was in the so-called "appendix" position, not the 4 oclock "kidney" position. I bought a flimsy Ace Case IWB holster & have happily appendix-carried ever since.
BTW "mexican carry" refers to not only holster-less carry but usually also to a 4-o'clock carry position. I guess if it was butt-forward at 4 oclock (heard of a few people doing this) it would be "mexican cavalry" carry?