I think I understood, Phil:
Looks not a huge issue for me, I think I'll live with a model that has a grill (once glued and filled) 1 mm wider...
BTW a solution may be to use the 964 3.8 turbo body: those vents looks more accurate and it isn't needed to fill the gap between the wing and the grill. Sure would be quite tedious to sand down the turbo trim under the doors.....