I have one of these Leinbachs on my 2305. Have made many holes w/ a 12" auger. The tractor has no trouble with it. I can get more than 3 feet depth, but don't know how much more.
It's a little scary when the bit first starts tearing up the surface, you kind of have to let it do its thing and not try to precisely guide it. But I've used it in all kinds of soil, rocks, etc, and it's given me no trouble at all. Did a flagpole base in my parents' yard, heavy clay. It caught and started screwing into the ground, lifted my front wheels before I could stop it. I set the down speed on the 3ph very slow when I use it now.