Well I discussed this with my dealer today (who happens to be a sponsor of this forum) and he stated it's fine, not a problem and he even looked at the same setup in his shop to confirm that.
What's interesting though, is that in GB's part numbering system for their saw bars, an SG designation = 10 sprocket teeth and an SL (I think it was) designation = 11 sprocket teeth. This GB bar is stamped an SG, but has 11 sprocket teeth (counted them more than once).
Either GB has deliberately changed this 20" 3/8 bar to an 11-tooth sprocket to work on a Dolmar PS-5100S, or I have a mismarked bar. My real concern is, however, safety. I tested the saw this afternoon in some dry firewood and it kicked ass.
Comments or advice? Thanks.