I'd try to mount as close to wheels as you can.
Your geometry differs, but adding a coupler to a Generals body, it would get pulled off the rails in curves double heading or pushed itself off pushing a heavy car. Mounting to the pilot truck stopped it. All the lateral forces go to those pilot wheel flanges now.
Like I said totally different geometry, a Gen. has close set drivers at the rear so the nose becomes a long lever, but you might want to rig things for a test before total commitment & holes.
I still cant push well because the coupler is long and swings to the side very easily, binding at couplers (claw) and derailing the cars truck at times. But double heading was what I was after, so..."sold".
Looks good though. Nice even rolls. Always sand, clean, AND primer metal eh 
Maybe even a brush coat of black(?) on the edges before the finish coat. Edges chip easier and hold less paint at the tip of the "point(s)" of edges.
