Bill, I think you're a little more optimistic than reality can support as far as room temperature super conductivity goes. The higher temperature super conductors do have higher limits to their magnetic field density, and if you break that bad things can happen, nothing I've ever read suggests any magical island of higher temperature feasibility anytime soon. They're still experimenting with new materials but even the behavior of these materials and the conditions under which they can maintain super conductivity aren't well understood.