Thanks for the advise. Hoping the 510 o-ring will be effective. Time will tell.
You said your running a single, I've noticed that if I over squonk with a single I can get juice weeping out of the closed hole. The hole in the AFC that does not line up with a hole on the cap.
If you look at the top cap without a AFC ring on it, there are three holes with an o ring above and below the holes.
When you over squonk juice can go through the two holes that don't line up with the external hole. This juice then sits between the cap and the AFC ring trapped by the o rings. It can make it's way to the 2nd hole in the AFC cap that does not line up with an internal hole and leak.
I've found that if I cover the hole that does line up with my finger and draw air through the drip tip it will clear this liquid out of the AFC ring.
Also I have 10 Reos, some I can run with no o ring, others will leak with the same RBA installed if I don't use an o ring. Put the o ring on, the size of the o ring should be selected so that the Nuppin seats with a nice seal against the o ring and the air hole is lined where you want it. If the air hole is not right pick a different size o ring. I use 1mm x 10mm or 1.5 by 10, some are also using .5 x 10. Then adjust the center pin to make contact.