USC makes good stuff but I have not used the product your speaking about. Metal 2 Metal is a crapshot. I have used it with good results years ago, but the last couple of cans we ordered were VERY thick and hard to mix the liquid hardener in correctly.

If you are just looking for a good durable filler for the sectioned area, I use Evercoat Fibertech. It's similar to Kitty Hair or Marglas, but is super easy to use and hardens like concrete with regular creme hardener. Cleaning up the area to be filled is probably the most important step, no matter what you use. You can also etch prime the area before you fill for added durability. Don't take my word as gospel as everyone has their own preference to do things. But in 38 years, I haven't had anything fall out yet.