We also tried the Slypner shoes and had a problem with keeping them on.
They cost me two days of the OT ride, due to the horse stepping on the
back of a baseplate and twisting the shoe. We couldn't get it off
(carry tools now) and I had to bring him on in with it twisted--lame next
day, naturally.
They are a good idea, but you need to get a perfect fit and that's
difficult to do, as like Linda said, they can't be shaped to the foot.
We now use the Werkmans, which are as strong or stronger than the St.
Croix Eventers and the nail holes are placed better.