Do 'true' dwarfs exist? I doubt it. It seems that most of the really small cherryheads imported in 1984 eventually, with lots of food and care, grew to be about 'normal' sized redfoots.
Having said that, I spoke to Joe Terry at the recent Expo and he insisted that one of his pairs is very small even though they have been in captivity for many years. But then, I have seen imported redfoots from Suriname and Guyana that were also unusually small for adults too. I think there are some that are just runts in any population.
As far as keeping the two forms together you can---but I would try to avoid interbreeding.