Jon ,
My friend sailed there in December and back in march or april .
He said December was worse ( Not sure why , Maybe too many headwinds ) , and back in was better but that may have been lucky .
I would say that Sept / October would be best time . How long of a stopover are you looking at , would you be able to pick your departure times at each point with a week or two up your sleeve .
Definitely then worst time I could think of would be from Nov all the way till July . With the possibilty of either a low spinning cyclone or ex-cold core low , and later into may /june the possibilty of an ECL making your trip hell .
If it was to be in that period ( march-june ) , I'd keep an eye on the upper atmospherics aswell as surface . As apparently ECL's will b picked up quicker as they come overland ! I know some Surf Guru's from up that way can call ECL's up to a week out by just looking at maps of Uppers , Sat pics and surface charts . ( Sans Models ) . But these days your'e reasonably safe with models ensembles providing decent forecasts . Regardless of these though , ECL's can be unpredictable .
Good luck .
Pete .
PS. Maybe check in , and PM some of the wiser users a week or two out from departure !
_________________________
Quote " If you want to save our world, you must hurry. We don't know how much longer we can withstand the nothing. "