Last night I got a short update from one of The Gray Mouser's new valets.
The Gray Mouser is calmly camping out under their bed, but he doesn't seem stressed. He certainly hasn't minded when the valets come by (down?) and pet him, and he's already come out to be cuddly at least once.
All that sounds much like how he was when he moved into the Kitten Farm, so I assume he'll be fine, and slowly will work his way into the new household (more than here, where the Catzilla brothers crimped his laidback style.)
Meanwhile, the Catzilla brothers are acting like they own the Kitten Farm, which, come to think of it, was how they acted with the The Gray Mouser here. But now they are exercising even more control now, for example snuggling Katherine even closer overnight.
Life seems good all around.