I checked the fibreglas resin on the flange of the snorkel late this morning, and it had cured almost completely. So I unbolted it and pulled it off. It took a pretty good whack with my fist to jar it loose, and one of the little spacers that go between the upper end of the snorkel and the baffle floor went flying somewhere.

The gap between the flange and the face of the fuel injection was completely filled. In the picture you can see where the edges of the packing tape pieces were - the ridges look huge, but in reality they are only a couple of thousands of an inch high - the paper gasket will take care of that. I've still got a bit of trimming to do on the edges of the flange, and I've got to go some filling and trimming to move the big hole where the air flows to the centre of the flange.