Roof vent covers over Fantastic Fans

I installed mine per the instructions by drilling into the plastic and using the self tapping screws. I think there is a hole you can add a screw directly thru the bracket into the roof if you think it's necessary. I can't remember if I did that or not. I did have to remove, then replace some sealant on the flange that was preventing the mounting bracket from sitting flush to the roof. If you don't want to drill into the roof for extra support, adding some adhesive between the bracket and the roof should help.