Thanks for the answer.
The survey did not highlight any problems with the rig. I took the mast out this winter to check everything was OK at the top, and to replace a few things.
I can't remember if it was like that before un-masting the boat, or if it was OK and the mast was not put back correctly.
The forestay is as tight as the furler will allow, which means that I know of no other way to increase the tension forward. The whole rig was replaced about 10 years ago, maybe the rigger cut the forestay a bit too long? I don't know..