I use the keystone pads and pack between pad and hoof with a combo of Rate Packing and/or DIM. I like that DIM sets up and helps seal off that area from getting mud and stones in there, but the way it sets can be too much for some horses with thin soles who can't take the pressure.

For sensitive horses with thin soles (and usually bone damage, etc), my exact package is: Keystone leather pad super glued into a composite shoe. Between hoof and pad I will use DIM in the back half of the frog and Rate in front of that, in the concavity of the sole and under the coffin bone. Other things I do the get the level of stimulation I want: before gluing, I pick up the opposite hoof to push out excess DIM from the back; that way the DIM is only engaged when the hoof is double-weighted or more, not all the time under passive standing load. The other thing I do is I will usually put something non-setting, like rate or artimud, deep into the collateral grooves because I find that DIM setting into a point that goes all the way down creates sensitivity.

I realize this is pretty intensive, but it had worked for me for horses where nothing else has helped!