I also did that the first time with our old Roo. I've learned since then to remove the plate at the end of the year before covering...don't have to worry about snagging it in the spring when taking the cover off. But my fix was to snip off the remaining plastic pieces flush with the brake light and then install a metal plate holder with screws into the body. I used gorilla glue and then sealant around the head. Much more sturdy than the plastic ears!
2004 Fleetwood Providence 38U
currently not towing a toad