We picked our feline crew up from so-called "kitty camp" this morning, where they'd all been for ten days. In consultation with the vet and one of our favorite techs, we decided to put them altogether when we got home--the basement gets colder with each passing week of winter and we were afraid the new boys would never voluntarily come up to the other floors.
So, when we got home, we left them all in their carriers for awhile, facing each other. And there was no hissing or anything. Then we let them out. Patron (aka Tabby) went downstairs; Mojito (we incorrectly pronounce the "j"--"moe-jee-toe") went upstairs (henceforth, M and P are now the NYCats.) Hermione and Albus (henceforth the CT cats) wandered everywhere. Their paths crossed several times during various explorations and there was NO HISSING or FIGHTING!!!!!! They even sniffed each other and just passed by, several times.
We couldn't have dreamed up such a great scenario so quickly. We did, at some point, carry Patron upstairs to where Mojito was sitting under Bud's bed (his favorite place, which he found on an earlier exploration); then Patron explored the upstairs for a long time, with the CT cats on our bed just ignoring him. No conflict. This evening, Mojito has joined Patron in the basement but also came up to say hi to all of us before going back downstairs.
And so tonight, we are not shutting the basement door so that the cats don't feel separated and we don't have to start over again tomorrow. We will however listen for hissing.
All of that and the fact that the vet couldn't find the small mass in Patron's abdomen that he'd felt two times before (I'll believe it's gone when the vet doesn't find it a few more time!) and there are no symptoms of trouble meant today was a really great cat day.