good luck, I guess first the ideal sail angle param, without a vane its probably best to be tighter(higher number) then looser, not that is has to be perfect, so long as it goes. tuning the steering is the same as normal,just is harder to judge because the speeds not constant. You should be able to set up a 2 point reaching mission with a do_jump waypoint to just reach back and forth while you tune the L1 nav controller. This is only used in auto when not going upwind (angles larger than no go angle + 10 deg). Then all modes should work. If its windy enough you could have a look at the sail control PIDs, these kick in at heel angles larger than the max heel, I would just add p gain to start, and keep I D and ff at zero. I think loiter should work too, I only found the LOIT_TYPE param on after i tested it the other day, has to be 1, so it knows to turn round not try and try and reverse.
This is my latest parameter set if its any help.
Pixwawk5.param (12.4 KB)
I lookforward to seeing how it goes.