Peter....it’s all down to the shape or profile of the top of the scuttle. It is too flat and as it doesn’t follow the curvature of the windscreen frame, the rubber seal does not sit firmly down on the centre of the scuttle.
Presumably you've tried putting a bead of silicone sealant along under the windscreen frame to seal it?
I have seen the silicone from an earlier attempt John made to fix the problem. I had assumed it must have been coming in somewhere else.
My new windscreen does have this problem to a small degree which just goes to show that the bottom rail of the windscreen can be a variable too.
If a replacement glass could be fitted perhaps a frame, without glass in it, could be "massaged" to fit better and then a new glass cut and fitted.
If John can get hold of the frame of a broken windscreen from somewhere it might be a possibility worth pursuing.
Raises two questions for Morgan: 1. why can't they improve the quality control of the shape in this area, and 2. if they can't why don't they have an (a) and (b) type screen so as to choose the one which gives the best fit.