Rainy Day Fantastic Fan Installation Blunder???

I installed a Fantastic Fan last week and, going by the You Tube video I referenced, I installed the foam gasket between the ceiling and the trim piece inside the RV. I did not see any directions relating to its use. I used butyl tape between the roof and the fan flange and placed Eternabond tape over the edges and screw holes. Can't imagine that foam gasket providing much protection against leaking.
This is the You tube video I referenced.