How did I do it? I installed it to a virtual machine in Parallels. The idea was that once I had the right operating system I could install it to a different disk (you know I mean SSD). No dice, the install failed. After the third trial I gave up. What did work was to clone the virtual drive by Carbon Copy Cloner to another disk, not an SSD, mind you (as that also always failed). But I did get it to clone to a hard drive, and THEN I could clone it to an SSD.
Mavericks has now been running for a few hours from the SSD without any of the problems that I had with Yosemite. I hope it will stay that way.
I suspect that Apple will close this hole soon as well. They seem to want everyone to march in lockstep!
Update at 10:00 on Monday. May 4: So far, so good.