I use 3M electrical tape to seal mine.Had the bonnet on my boxer up today noticed top of engine very wet,on close inspection rain is getting between the windscreen and the moulding tat forms the gutter,on pulling the moulding away from the glass a few mm "muck and moss" between the 2.having tried various rubber mouldings have come to the conclusion the only thing to do is bond the back of the gutter to the screen where it won't be seen...maybe worth other owners having a closer look
Been into the dealers three times and last time they changed the whole scuttle. When I checked it with a hose it was still leaking so back to the 3M tape. Ill not bother giving the dealer another chance.