He is two. He may very well bulk up and I believe it has nothing to do with him being a stud or gelded.
: ) So if you want to de-brain him I say do it before he realizes what he's got and how to use it, lol.
I agree! I think it has more to do with genetics. Some gaited horses just seem to have that lanky conformation. I have a 1/2 Fox Trotter, 1/2 QH colt and everytime my vet sees him he says "that's going to be a big horse" and I gelded my colt at 5 months. I have read they will get taller if gelded younger. Not the same as being bulky, but an extra inch never hurt no one.
At age two, if you are planning on gelding, you might as well get it done.
I am surprised he is not acting studdy already as have a neighbor with a colt born a month later than mine and she didn't geld him until he was 8 or 9 months and he was already acting studdy and showing interest in his mother.
So I'm glad I got my guy done before he started showing interest.
On the plus side, he may still tank-out if it is in his genetics even several years from now. The same neighbor had a Fox Trotter that was so narrow (dare I say ugly) when I first saw him and he was aged 4. Several years later and he is much wider in the chest and quite the handsome dude! So it took him a while to broaden out.
So I don't know if your horse will tank-out or not, but it is likely genetics more than hormones. Even tanky gaited horses don't seem to have the butt of a Quarter Horse though. My Fox Trotter mare is very broad in the chest and "okay" in the hind quarters, but she will never be a QH muscle-wise. I think it has to do with form following function because most gaited horses are built quite different, especially in the hind quarters, than stock horses are.