Here you can see the final installation with trimmed cowl. I'll use rounded screws.
I ordered proseal and will use it to glue and rivet on the aluminum brackets to the snorkle. Note I made one for the front too.
Then I trimmed the bottom of the snorkle to square.
Photo three you can see I applied ProSeal in the corners and to all the mating surfaces when I rivetted them together. Also note I used solid rivets instead of the pulled rivets that came with the snorkel kit. And I bought another piece of that S shaped trim and applied it to the front.