Bed question

First off i gotta say the first day of the magnetic mini bash was the shit, got to catch up with some poeple and see some sick rides.

My question is about a dip in my bed. The center between the wheel wells dips down and im pretty sure that it will still be there even after i get a spray on bedliner. I dont know if it can be hammered out because i havent taken it off, but i wanted to know wha would be the easiest way to fix this problem?