I think 20 some kitties would fit in fine. In the second and third pics, the building to the left is our 'kennel' building. Has heat, indoor/outdoor runs with communicating doors, and a screened in porch. Ready for immediate occupancy since the dogs never use it.
If I put the dogs in the house for safety, I'll bet I could fit nearly 10 or 11 of the kitties in the leaf hauler with me on the way down the hill, too!
Think they'd still be in there with me at the bottom of the hill?
FG, that pic was actually taken a couple days before the rest, but it was so cute I just had to find a spot in the story to show it off.