Nothing like a dummy foal or lethal white, but research shows that all silver dapples have eye issues. Doubling it up causes MCOA. However, most horses with it have few to no problems. I'm pretty sure it's fact at this point, not something they are still looking into. Unless you have your horse color tested there is a chance that both your mare and the stallion are homozygous, and both have MCOA already. You probably would never know. It's a decision you have to make for yourself, and some people are wary about buying a horse that they know is a double. But no one ever talks about not breeding rocky mountain horses because of it.
