When it's clean, I use a Joey in our lone Nikky on Spike-o. Great, trim fit and no leaks. Of course, Spike isn't a pee-meister, so if you're kiddo is a heavy wetter, you might run into problems.
If only Nikkys weren't so darn expensive . . .
I also "made the mistake" of getting two dozen premium CPFs and have found yup, they're kinda bulky. They fit fine in all the medium wraps I have, but after I used the lone infant CPF I have in a cover, I felt like I've been wacked with the idiot stick. Duh, Spike-o's just about 15 pounds, and some people have used infant-sized CPFs on their kiddos up to 20 pounds. Hopefully the smaller dipes'll arrive soon.
Good luck with the AIOs!