No, it can't be the hinges - my first sail had them too :)

Along the way I have thought about building a totally new and big, stern-hung rudder. This would free the space to make an outboard well - the light bow also means, that with an outboard behind the stern, it is almost impossible to motor in a chop. 

Thank you for the analysis, Arne. 

Your diagram is right, although at the moment I have dropped the top panel. I have already tried moving the sail back and forth, the balance changing between about 20cm to 60-80 cm. The latter was one of the reasons to drop the top panel (to get a lower angled yard).

At the extreme end I can see and feel the nice camber being severely destroyed by the mast (port tack) and mast lift (sb tack). But this is no news to anyone :)

You described the hull issue excactly like I have thought but wasn't able to describe. The light bow is very sensitive to the weight of the rig, especially when pressed harder. It was apparent with the bermudan rig, but the drive was so much better that the boat could handle waves and headwind with a lot less pressing (like I said, a lonely, small storm jib could do the job). The BR mast was also very light.

The rig is the only "extra" weight at the bow. I have a hanging 25kg outboard on the stern, a stainless steel "targa" above the pulpit, extra fuel and two anchors at the back. The battery and water are located in the space for the inboard motor (which I never had). 

Like I said, there is a possibility that there is no way of getting the boat sail well enough for my purpose with an unstayed mast this far forward.

Of course, its also possible that my sail has been cut, sewn and rigged in an inferior way, despite of your excellent plan. This is something that I have no qualification to estimate. The more excperienced sailmakers will have to evaluate it from the picture/videos.

EDIT: Concerning the rudder endplates, it wouldn't help the lack of drive vs. sail area issue, right?

A thought: is it possible to trim half a metre off the leech of your sail?

This would move the camber further back compared to the chord, right? I'm sorry, but I don't understand how this would be a benefit for weather helm and loss of drive issues.

An interesting offer, David, thanks!

I wonder if the length of my mast is enough in it's present length, though. How much would I need above the deck?

Buying a sail hasn't crossed my mind, but in case someone bought my sail for a price that would be around the price of yours, this would be like a lottery win.

Time to analyze the situation and why I'm in a process of possibly selling the sail or the whole boat. I have to emphasize that my understanding of aero- or hydrodynamics is absolutely nonexistant. I just reflect my thoughts with the experiences I've had.

The sail works basically as it should, but there are things that in my way of sailing just don't seem to be as I would like to. Many people would be happy with the boat and the rig as they are - and I would be too, if my sailing environment and needs would be different. I have a hunch that many of the problems depend on the hull, which is very easily driven, but also has a very light/narrow bow. This might mean that the boat will never sail as well as I would want to with mast as far forward as I have moved it to.

Problems:

1) Excessive weather helm, especially in harder wind. Yes, this is the situation in most small bermudan boats too. For me the problem is quite severe, because of some other thing (read on). The aux-rudder/self steering has helped a lot, but not enough.

2) To fight the weather helm, I need to move the sail forward for lots of balance. This in turn destroys the sweet camber the sail has and also drops the boom (because of the high-peaking yard) lower than I would like to.

3) Too much sail area/chord length. As such this is not a problem, because of easy reefing and because I can take off one panel at a time, thanks to the structure and separate panels of the sail. Since last year, I have cut the mast by a meter and left one (of the 7) panel away. I have tried leaving away the lowest ant the topmost panel (one at a time). Again, read on. 

4) The size of a single panel is too big, along with too low AR. It's very usual to find myself in winds - other than gale conditions - that need reefing to three or two or one panel/s. And remember, the camber in the top three panels is very low/zero.

5) Because of 2) and 4) I just don't get enough drive to sail properly in harsh/ish conditions, especially on waves and against the wind. The boat gets stuck and doesn't tack. This is a big problem, as these kind of conditions are very common in my sailing waters - along with narrow passages between islands. 

I would't be as tempted to fix this problem-package, if I didn't have experience with the boat as bermudan-rigged. Using ONLY a tiny storm jib, the boat climbed happily along, above big waves against the wind, and at an unbelievable angle. So, the hull is excellent as such. 

My options:

1) Leave everything as is, and try to learn to live with it.

Pros: cheap. Cons: takes more buddhist attitude than I probably have.

2) Move the sail back to get good camber. Add a flying jib or two (with a bowsprit). Maybe shorten the two top panels along with this to be able to use 2-3 panels with jib/s in harder winds.

Pros: fighting weather helm, getting more drive. Cons: more complex, more stress on the mast (although I think my mast is a bit overkill anyway).

3) Selling the sail and making a new one. Options would be a) a shorter chord/higher AR, maybe with a jib b) some kind of a wingsail with a shorter chord c) Split junk.

Pros: many problems MIGHT be fixed. Cons: selling the old sail, making a new one.

4) Selling the whole boat to someone with different needs than mine. Although selling a JR boat in Finland is probably undoable for a reasonable price.

Pros: a fresh start. Cons: Sad. Many good things lost with the boat (accommodation and headroom compared to the size, shallow draft, good potential for a well-sailing boat and an easily done unsinkability). A lot of work with the hull being lost (The mast + partners, bottom job including sealing all through-hulls, epoxy coating, making a composting toilet, watertight companionway etc). 

At the moment options 2) and 3) are on top. 4) also has awoken some interest, because I have spotted a few cheap boats that are kind of intriguing. But I try my best to resist.

Any ideas would be appreciated. Please help :)