Frederik,
I hope your new toy will not disappoint you. The sailplan, slightly modified from Ingeborg's, should hopefully give next to neutral helm. Remember, there is room for shifting the sail a bit foreward or aft, until you are happy with it.
One thing I should like you to do, when Orion is up and running, is to measure the actual depth of camber in each panel. I have forgotten what I recommended, and anyway, since Sebastian uses the shelf foot method, the result may be a bit more or less camber than you prescribed. In my Ingeborg the camber initially turned out to be just 7%, but then I eased the tension along the battens 3-4 cm, which resulted in 8% camber, just as I aimed for.
Good luck!
Arne
(Member's album Section 8-9 of photos)