I will modify the lid myself possibly using some silicone so that the silicone will sit on top of the basin where the grid is providing a seal, but I think a fix wants to be thought of for "retail".
A really really bad sketch to demonstrate where the gap is;
The fully glass lid won't have this problem as it is the same thickness all over - and so the entire lid sits on top of the basin leaving no gaps.
One fix for this would be to have the grid on the *underside* of the glass lid - not on the "top side".









2cm is a little small i think, better would be 4 ore 5cm
