With a camper shell on my 2010 FX4 it's a little hard to tell but is front (cab end) of the pickup bed double walled? I was planning to install a couple of bicycle fork mount brackets on the inside of my bed with sheet metal screws but I'm not sure if it's double walled or not. Any idea how long of a screw I can use without making a pin hole cushion out of my truck?

 

Front of bed is not double walled, the rest of it is.