I know epoxy has a bad rep here now that ETI's application has had a couple failures but if you are interested this video shows how to properly apply a fillet to the sides. Keep in mind for proper adhesion, you need to rough up both the aluminum and the trailer. As I've mentioned before removing the gelcoat is recommended by West System, but not practical.
If I'm seeing it right, if you look at the images of the OP's trailer (other thread page 3), the panel was mounted just to the rear of the apex of a 5.0 roof, could not have found a spot to get more wing effect then there. The newer installs all the way to the back, behind the air conditioner are much less susceptible to the wind. A sub par epoxy job like Bob's could compound the likelihood of a failure.