Mate, maybe it would help if you looked at several of the posted pix in the ad: the boat was NOT launched (or designed) with a sailing rig. It appears to have been an add-on, perhaps for the trans Atlantic passage
. It is most certainly meant to improve fuel
economy on some points of sail and in some wind
strengths, not to sail on its own.
Sure, it will blow downwind slowly, probably up to around 140 or 150 degrees true, but to describe this as "sailing" is stretching things.
Another way to look at it: They put hundreds of BHP in the boat to motor
her along, and it takes a LOT of sail area to equal this... far more than could possibly be flown from the short and ill-placed mast
, even with your proposed big screacher.
In short, give it up... ain't gonna happen.