hi billmc!
great work!
you are reminding me of what i went through with my 1.5hp conversion. actually had a 11 foot prop on it and all it would do was stall very soon and badly. that was in the 1 star connection. basically, it just hit charge voltage to soon and the prop could not exceed what the genny was putting into the 12 volt batt i was using. i was limited to just a few amps output (stalling).
you will probably find that 2 delta will yield you the best performance as it really allows the prop to speed up and have lots of watts available. however, you really miss out on the lower wind performance. you may find also that the prop will still stall in the 2 star connection, but with a little more output as the prop can run a little faster before stall.
in the end after you confirm just how it picks up speed in 2 star or 2 delta, you will i think agree that a star/delta switch will help get the best of both worlds.
i know its a little work to lower the mill and re-connect trying the different connections, but it really does open your eyes and make you understand the relation between prop/speed/cut-in and overall performance.
don't be surprised if you see your mill hit 500-600 rpm with strong winds as i can just about guarantee that you will. i also suspect you may find your mill giving you 750 watts plus.
hope your prop is well built and balanced. you will find it scary at times
have fun,
zubbly