I really have no idea, but I suspect there would be a lot of ‘it depends’ in the answer.  One factor might be that wind speed generally diminishes as you get closer to the water.  So an IMF main in the upper position would catch slightly stronger wind.

—Peter  

> On Feb 22, 2017, at 10:24 AM, Joseph Doucet <jadoucet at snet.net> wrote:
> 
> OK, I agree on the heeling issue. the boat will sail with less heeling with the IMF sail in the lower position.
> But in moderate wind ~ 10 knots, does it sail faster in the upper position or in the lower position?
> it seems that in the lower position the genny covers more of the main so it may provide more drive.  This may depend on whether one has the 130 or the 175 genny.
> Thoughts?
> joe with the recycled 2004
>