Did you get a chance to see this one through? We have a quarter crack horse with a coronet band injury and I've tried many things and it hasn't closed up. Never tried casting or this sort of repair. I'd love to know how this went if you were able to see the repair through to the end.
Sorry but that heel needs to be floated or that crack will never heal. Use a frog support pad cut pad away from side clip back to heel the width of the shoe under the crack . Put equi pak under pad, put play dough in floated area so not to get any equi pak under your float. remove play dough after equi pak cures. no patch needed. This will float that heel 1/8.
