I was chatting to a mate about how I didn't understand why the bonnet seal gutter channels water INTO the engine bay and ONTO the bulkhead. He suggested I do something about it and so I did. Two small bits of rubber glued onto the ends now channel most of the water down the outside of the wings. I popped a little seam sealer in to stop all that water creeping into the join by the edge of the bulkhead. Simple job - probably less than an hour to do both sides.