Deep all the way for Cheeky. He really feels the ground, and if it's hard he panics and gets quite uptight with really choppy strides. He loves mud though, and really goes well when every other horse is skiing round, slipping everywhere.
My yards surface is quite deep in the corners and my horse sometimes struggles when it's wet but when it's dry it's fine. However i would prefer it was a bit harder, not too hard though