Thanks a lot for all the replies and sorry for the somewhat late reaction. I have been busy taken the wings off to get them painted, because the filler on the rims came off due to the tire rubbing the edge. It is clear that we all wonder why the factory did not correctly positioned the rear wheels in the wheel arches. In my situation I cannot even correct this, only if I would mount a smaller/different petrol tank. As Simon (Sifab) writes, an expensive solution. I also don't want to get back to the narrow tires.
First I am going to try to move the wings 10 mm outwards. This is possible on the front of the wing and at the rear there is approximately 7 mm space to move outwards. This way the tire will not rub the inner side of the wings. One of my Morgan friends suggested to have the wheels re-spoked, moving the center slightly outwards. This way the wheel will move inwards. It could be a solution, but also not cheap and it is difficult to find an expert in The Netherlands that can do the job. The last one I know stopped some months ago. Conclusion, I will try moving the wings outwards and if that doesn't do the job....new tires....??????
