I main husngs. I just recently moved up to the 33 turbos on FTP. 30BI is a fairly standard BR for regs/turbos. I generally play by the guidelines in this article:

(I can't post a link, but It's on HUSNG.COM, it's under the free tab of HUSNG under articles, last article in the list titled "Bankroll Management")

I tend to be a bit nitty with my BR though, and currently play to 50BI before moving up. I think that playing with 60-100BI for superturbos and 4mans is fine too due to the increased variance.