Arjan, so the upper half of the top of your new mainsail is a little flatter then your old sail.
I'm puzzeling at this moment what consequences this could have. It's in the part of your mast which is not supported by shrouds anymore, so the part that bents.

Overall you measure about 10 cm luffcurve; that's not a wrong figure. But it depends ofcourse of your mast.

I used to sail to sail on a (soft) P15 mast a mainsail with 15 cm curve. But then I changed to a sawn-off P18 mast which was very stiff (curve 1,5 cm). I modified the sail to 11 cm curve, but it was still far too much.
Now I sail with a main with 7 cm luffcurve and that's perfect.

This doesn't help you much but give you perhaps a little bit of feeling for the figures.
The difference between the mastcurve and the luffcurve of the sail is considered to be one of the secrets of the sailmakers; they all use their own secret number. It is indeed about centimeters.

Maybe your top cannot open enough?. Looking at your original video of this thread, I see less twist in the upper part as compared to my sail. I know that a lot of sailors think that a flat and tight sail is the best. But without movable waterballast like on the Imoca boats, twist in the sail is our only safety valve for overpressurizing the sail.

As you can see in the little vid which I placed in the thread about jibreaching, I have (at the ingoing course) also difficulty too to keep my leebow not to be burried in the water.