Kirt,
I know this may be a bit of a pain but have you tried to
trim the spinnaker with the tack pulled over to the windward bow.
Seems to me like you may get a greater forward component in the drive being generated.

If you have I would be interested to here what you felt as the difference.

Just a thought.

Regards,
Phill

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!