Two words: taller collar.
I have two of the shorter 5-gallon Torpedoes and they fit on the hump, whereas the slimlines do not. Using the slimmer Torpedoes or regular Corny Kegs I can get four on the floor of the keezer, two on the hump.
Those are good tips, but yeah I don't think something like that will work for my setup. My goal is to get everything built in under the counter. I had another thread about that here if you are curious:
https://www.homebrewtalk.com/showthread.php?t=629532
Since I tend to prefer to do more frequent but smaller batches I think the 2.5 torpedos are a good solution. I should be able to fit two in either the standard or slimline, but the exact height will make the difference with getting an extra shelf for other storage.
If it were a hair under 22 inches I could fit at least one five gallon without having to worry about significant modifications.