Hi Sailmaker.
In answer to your questions.
The line for the sails sheets. 25kg Dacron from Sailsetc.com will do the job nicely.
http://sailsetc.com/fitrig.htm# product no D25. 20m spool for £2.25
How far should the sails be out. Well this is how I set up mine.
Stick full back and the trim also full back.
Main sail about 10-15 degrees off centre. If central she won't move anyway.
Jib about 5-10 degrees bigger than the main (i.e. 15-25 degrees). It needs to be offset further than the main (your picture looks the opposite),this creates a 'slot' for the wind to accelerate over the curved side of the mainsail increasing power.
Stick full forward and trim full forward should have you touching the shrouds.
Don't worry about the sail arm, you can make them out of a piece of ply or plastic. I think Martin used a plastic ruler on his sailer.
Regards straight line running. Yours may have been affected by your jib setting trying to swing the boat around with too much pressure up front in balance to the rear. In effect she may be on the point of broaching.
Additionally, as she heels over the water will run around the hull profile. So if she is heeled hard over to the right, she will want to go left. This can be mitigated by a little bit of right rudder (this can be done with the trim). But if he is heeling over to the left, everything is revered (including the direction of the trim). Easily sorted
When you do the refit, go back as close to the manufactureres instructions as you can. The boat has been on the market for years, it has a good reputation
, I think Robbe will have set it up nicely. I think it may be that veering away from the manufactureres instructions was the beginning of some of the problems you are having now.
But there is nothing major wrong with your boat. It just needs tweaking.
Try resetting up your sails first and see how much better she sails.
To give you an idea of the improvements you can get with a longer sail arm try this. Set it up so that with the stick full back the sails are already out 30-40 degrees (jib a further 10 degrees out). This will give you a better idea of how well she will sail when she is not heeled over heading into the wind, but doing a nice broad reach, and running