Fiberglass Thin Spots

Hi Everyone, I was finally able to get the top panel removed from my starboard hull on my Mystere 6.0. Good news is as far as I can tell it is watertight. I shined a light all over and didn't see any places where the light comes through. I did however see some thin spots that look like sloppy repairs from the previous owner. They don't have any flex but I wanted to strengthen them a bit before I reseal the hull. I was think of sanding the outside smooth after this guy's previous attempt and reinforcing with Bondo Glass. Another thought was laying a strip of fiberglass cloth on the inside and leaving the outside alone. or a combination of both