Just chiming to agree with others saying there are no hard and fast rules about this stuff. It all comes down to personal preference/comfort, etc. I played things more closed, more open, and ended up kind of in the middle (7/7*). If what you're playing on currently works, keep using it.
One last thing, unless the baffle/chamber characteristics are vastly different you will be surprised how similar you sound on different setups. I notice a different difference in the response and volume than my actual timbre.