Ok, to prevent people from being able to browse you while on Himachi go to Control Panel >> Network Connections and then you should see Hamachi in the folder. Right click on it and go to properties. You should then see a checkbox that says "File and Printer Sharing for Microsoft Netoworks" You'll want to uncheck that box. Then press ok and your set! Thanks Android Data for this information.

Also, I guess there is a limit(16 I think unless you are a premium member or something :s) to how many people can be on the same Himachi group so we can just make multiple groups EX: BYOND, BYOND2, ect... and I think that'd work, you can be in multiple groups at once.