Stavanger, Tuesday
Richard, I agree with Paul.
Rule no one is that the halyard should not be attached much forward of the middle of the yard. or the sail will misbehave badly when setting and lowering (being tail-heavy). The best is on the middle or just a bit aft of the middle.
Rule number two is to avoid that the halyard angle gets wider than about 30° out from vertical with the sail fully hoisted, or you will need to haul very hard on the upper luff hauling parrel. This could lead to chafe on the mast and lots of unnecessary stress on the yard.
To avoid these problems, you have the choice between raising the yard angle, making the masts taller or increasing the balance. As you can see on my signature photo to the left, I have raised the yard to 70° and cut the mast short (it could well have been 20cm taller). This lets me keep the balance below 15% to reduce distortion of the camber when sailing on the port tack.
Good luck! Arne
PS: Finally, I advise on making the sails with nearly the same area in each panel, or with a bit smaller panels in the top section. The top section is the storm sail, you know.