Pressure Group X
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Right now I use an Atomic SS1 as a secondary.To echo what has been said, just seal your B2 and go dive it. A side question, what is your backup second stage? IMHO having a backup second stage that is equal to your primary second stage is important when diving. I ask as you mention using the B2 as your backup in the future.
I am going to go to a traditional reg as a secondary though.