I apoligize if I came off sounding "snippy" of my trimmer. I think it's more a matter of not understanding the many possible effects of EPM. Which, I guess, is a good thing. I would have preferred to go through life without knowing about it, myself!!!!
No apology necessary.
About the stocks, it has crossed my mind to build a sufficiently stout support structure, such as an "A" frame used to pull engines, etc., that I could use, along with a wide strap web harness of sorts, to offer just enough "lift" to reassure the horse. I've pictured it powered by either the winch line from my ATV or the frontend loader of my tractor. It probably sounds like a lot of trouble, but I feel I owe it to this horse to do everything possible to provide proper care for him.
Building stocks can be tricky business and getting a horse accustomed to them is not for the faint of heart. Frankly, it can be dangerous. Exercise more than a little caution and don't underestimate the power of a horse. Determine what you think represents a strong enough stock, then make it even stronger than that.
Make sure any straps you employ are attached via quick-release connectors. If the horse panics you want to be able to release the animal as fast as possible. When training, do so in small, frequent increments.
Also assure there is a mechanism in place that allows the farrier to easily restrain each of the animals lower legs. Never tie up more than one leg at a time. I can't stress enough how dangerous this process can be for the horse and the farrier if done incorrectly. Done correctly by an experienced practitioner, the process can be both safe and effective.
Besides, no telling what else I could use it for around the place.....loading equipment onto trailers, into the bed of trucks or even a skinning rack!
I understand your design thoughts but most stocks designed for horses are quite different than what you've described.
Here's an example drawing you might want to review. Do you need Horse Stocks?