F150 aluminum bed and sliding 5th wheel bracket

OP....You are not giving much info, as to bracket type (sliding?). Has the installer used this set up in other aluminum bed trucks, to know if it will work?

Are you referring to Reese standard rail mounts? Is the other Andersen bracket you mention, a rail mounted Andersen hitch?

With a little more info, or picture, you may get more, and hopefully better responses. We all know there are FW hitches installed in some F150s.

Jerry