Sealing Fantastic Fan & Canvas

I'm about to put the Fantastic fan onto the roof of my camper, but I'm not sure how the canvas wrap will work with this. The RV parts supply guy that I bought the fan from says something about using a foam ring (which I thought was part of the packing material - the directions are pretty minimal - it seems more likely that it would be used on the interior), and then this rolled up tape-goo that he sells. That would be topped off with some self-leveling stuff that comes in a large tube, which I'm not sure is necessary.
I'm wondering how to then wrap the canvas around the base. I figure that the canvas would go up under the dome, but it doesn't seem like TB2 would stick to the plastic fan exterior. Use Gripper? Then there would also be gaps in the corners where the canvas would have to be patched.
I searched, but couldn't find an answer. Any tips?
(Yes, I realize I have to put a wood block in the left side corner.)
I'm wondering how to then wrap the canvas around the base. I figure that the canvas would go up under the dome, but it doesn't seem like TB2 would stick to the plastic fan exterior. Use Gripper? Then there would also be gaps in the corners where the canvas would have to be patched.
I searched, but couldn't find an answer. Any tips?
(Yes, I realize I have to put a wood block in the left side corner.)