I have the same problem. Mine is a coastline and leaks at the cornes on the hinge side. Acording to Lewmar a new seal can be fitted but i do not think that will help. They say that and I qoute "If the back is distorted the new seal may not make any difference. The back of the lower frame has been known to twist if the levers are left connected before the lower is bolted down." They also say that the bolting process should have fixed things.
In my case the hatch to lower frame seal is not "thick" enough. I am sure that a seal from their new hatches would fix the problem. But havn't got that far with Lewmar yet.
Another fix would be to glue an extra rubber seal under the original. This should be possible since the original would seem to be fixed to the hatch on it's outside edge. But one should not have to do that on a hatch of this age.