O.k. let's talk cats in carrier bags, as in, just how big a cat will fit?

I've checked the numbers, and most say a) underseat height is about 8 inches and b) cat must be able to stand up and turn around in the carrier.

Cat A is 13 inches at the shoulder when standing, Cat B is 11. 5 inches. Cat A travels by road in a medium dog carrier.

What I want to do is fly from PHL to MCO and drive back (spring repositioning rates). We've got a pet-friendly condo while in Orlando so they'll be o.k. there, I'm just concerned about getting them there.

Why I am taking 2 cats to Florida for 10 days? Cat A has gotten quite sick at cat hotels, and if we left him for 10 days with 2 visits/day from the cat sitter, he'd either shred the house, go into a terminal decline or both. Cat B would merely sleep for 22 hours/day, spend 1 dining and the last one harrassing Cat A (and losing).