A 1500 can handle 1-2 horses in a smaller trailer just fine. It will struggle with 3 horses if you go up a grade, the horses happen to move a hoof etc. 12k gets to the limit faster than you think. The weight of the trailer, each horse, each piece of tack, feed, water etc. Pay attention payload as well as tow load weight. You can’t max it all out at once and the throw in live weight. I give each horse 2000 pound credit to factor the one that decides trailers are dumb and the reactio