I had 3 Vamps and 3 RCC in a refugium under a tank once, I have no idea what I did to breed them but I got babies about 7 months into keeping them.
Then most of them got eaten, and they all died off eventually, never had success breeding them again. The biggest RCC I had was a little bit bigger than 3 inches, I think I might still have a picture of him somewhere if you want it. He died one day after climbing 6 inches straight up glass and crawling away to dry out in the sun.
RCC I tried again with, since they're cheap, and I've only successfully had one batch of eggs. It's really hard when you don't know what you're doing and are just going off intuition.
Sorry if my post doesn't really help!
Tank parameters at the time were:
Ammonia, Nitrates, Nitrates - close to 0
pH - 6.7
kH - 4
gH - 4
Temp - 75 ~ 78 F
Co2 - None