Frederick, do you know if that product is readily available? Or is it somewhat of a speciality item?
With the coming of the rain to the central valley, we too have a wet spot under our aft Fantastic Fan.
When I FIRST noticed it, I did get the ladder and took a quick Look-See... nothing APPEARED amiss on the outside, but clearly something is. Drip is right onto the dining table.
We want to get out for AZ on Wednesday, so I **MAY** have to live with it until we get down there, and then strip it down and deal with it then. We are supposed to have RAIN, RAIN, RAIN for the next week or so up here.
If the vent itself appears to be sound, then I would remove it, clean off all of the old sealant(s), and reseat it in new butyl tape, and caulk all of the exposed fasteners with C-10 sealant.