I have a similar problem with S. barbulatum F/Valle Quazarro. It's a beautiful, mini green Sempervivum and, as I understand it, a naturally occurring hybrid (barbulatum denotes that, but I am not certain at this point due to my ratty memory). It's about 1/2" typically, although some rosettes can get larger.
IN the spring, it puts out a ton of offsets, but it seems the offsets only last a year or two, then it goes into a population crash. If you catch it at the right time in its population cycles, it makes a great clump, but the clump doesn't last.
I'm going to try crowding it to see if close quarters populations will make it settle down a bit. I like all the barbulatum's I've seen so far.
A couple of pics:
