Thomas,

I think the ideal would be to have the CE 10-20cm further forward. That said, if the boat were mine, and the mast had to sit where you have put it, I would give it a try as it is. A finkeel plus separate rudder design needs less lead than a full keel and integral rudder design.
I would have a plan B ready: In case the boat turns out to have an annoying weather helm, I would start with fitting a big endplate to the existing rudder. I am pretty confident that this will help, but there is also a possible plan C: Make a new rudder and fit it to the transom.

Good luck!

Arne

PS: I hope you make the sail with some camber in it.

Thank you for your reply, Arne and David.

For the camber,  I think I prefer broadseam, for the simplicity of the batten.

Thomas, pardon for butting in here.
Both proposed sailcloths will work, but I would no doubt choose the lighter one at 172g/m². This will inflate and set better in very light winds.

Camber.
More important is that you make the sail with camber in the panels. A sail with camber in it will perform a lot better than a flat one.

I suggest you let David specify the construction of the cambered panels. The challenge is to make the sailmaker follow David’s instructions...

Arne

Thanks David, I've just scaled the sailplan to 24m², it gives something like that :

The mast is very long, I'd liked to make a birdmouth wooden mast but perhaps it will be too heavy.

Hello, I've just bought a Primaat 24 in need of restoration, without a rig, and of course I want to put a junk rig on her. She's a 24ft plywood boat, approximately 1.1t of displacement. Not sure exactely what type of rig I want, perhaps a weaverbird style, 24m² (the same area as the original rig).

I have a bit of work before starting the mast step or the partner, but I've started to think about the conversion. I hope you will help me with the rig !