Your R and D question is a valid one Mark, only if you are accepting a naked mirror. But if you drop several thousand dollars on a large scope, like the 18" Skywatcher, and you look to recoat, you are in for a world of pain. And if you buy one second hand, and also look to recoat, you will get a very nasty surprise.
This is a significant problem. Conical mirrors are designed to be fixed onto the anchor points with epoxy resins. Great idea, but a terrible option for recoating. "Built in redundancy" gone mad here. I would never consider an 18" mirror as disposable. I wonder if this point was considered by the mirror producers?
On another point, it strikes me as funny that these conical mirrors are made to safe weight, and to a lesser extent faster cooling, but the new scopes using the mirrors also sport bloody big counter weights
