I fitted a bunch of o-rings around the spiggot of the 2nd stage where it fits into the adapter. I did this after the body of the previous Omega 2nd stage cracked, where it had obviously taken a knock and had no "give" because of the rigid glue used to fit it into the adapter.
I find this method seals fine, and also allows the 2nd stage to move in the event of another knock. In the pic, the o-rings look too thin, but it's just a trick-of-the-light they do actually seal.