I am having the same problem with Tubster who is maybe 3 at the oldest.
I am going to leave him in the basement with a litter box when its cool , or on the porch if it ever gets warmer.
But I have to be firm, and not let him out as that was the reason I took him off the street in the first place to save him the fates of the Porch Angels.
We can hardly wait to see those Black visitors.