2 in front, 1 in the back, always.
reasons: front feet need perfect lateral balance, they take the brunt of the landing forces over a fence etc. front tendons are the most easily injured part of eventers in my bitter and extensive experience, anything i can do to lessen the chances of this i'll do. having 1 stud in front makes the foot land at an angle on hard ground.
for hinds, a lot of horses slightly twist the foot as it leaves the floor on every step (watch from behind in walk and trot) and i think 2 hind studs creates huge shearing forces on the fetlock joint, whereas 1 stud only anchors the foot in 1 place so can be used as a simple pivot, won't prevent this twist at all.
as you can guess, i've thought long and hard about this and interrogated a LOT of farriers!
Thank you for that, I don't really want to stud this horse infront, as she does suffer with her front feet, but I thought studding her hind would help her. And everything you have said makes sense, going to talk to my farrier and see what he has to say. Thank you...
TBH the most important thing however you stud is to make sure you stud according to ground conditions..... I never use studs infront on good-firm going and will only use one behind on harder going.... and the size of studs is very important too IMO
I use 2 in front because of the lateral balance thing mentioned earlier, & none behind because she isn't shod behind. Works really well for us, though don't think its in any manual anywhere.
If I stud in front I use 2, and when I stud behind, again 2 after a long discussion with the farrier guru. If am dressaging then will just use 1 in the hinds.
I dont really like to stud in front though