So, you will be sailing your B-20 on Lake Champlain I suppose.
I think that it will be an ideal boat for getting into some shallower areas that others cannot get into with the centerboard/swing keel set up the B-20 has.
I spent some summers up in the ADK's at a camp on a small lake near Whiteface Mtn. and my memory of the winds up there in summer was that it could blow like hell or (mostly) not much. There can also be some quick wind changes coming down from the fairly nearby mountains. Make sure you can reef the main sail in case you get caught in something and have a smaller jib handy just in case. Otherwise having a good working motor can save you from some grief. Champlain is a pretty big body of water and can probably get some nice sized waves if the wind is up to the task.
Still, the B-20 is a well made boat and should be up to the usual conditions there. The double sheeted main (if that is what it really is) may really be just one sheet that you treat more like a traveler; in other words it is not really 2 separate pieces of line but 1. It is a similar set up that I have seen on a Beneteau 51' and if you rig it up correctly I am sure you will figure it out. If not, ask more questions.
You have a great place to sail and explore so enjoy it and treat it well!