Doing more thinking. I know my ideas may not be good, but thinking about bad ideas have produced good ones.
The fact OP wants to haul outside bed implies some weight in bed. Then TW will transfer some weight from front to rear axle, plus more than TW to rear axle.
On any truck, the axle least likely to be overloaded is front.
If going to build custom hitch, build it to mount on front. Still need 2 point mount*, but that extra 400-500 lbs will not be messing with trailer.
Do you need to mount at 2 places? To slide into the receiver, you need play on side and top. Call it 1/16 inch. (Likely more) How far above the tire rail is SOG of bike? Plus rail will be above mount. I'm betting that SOG will be couple feet from mount. So that SOG will move well over inch. With inch stroke, a 300lb hammer can deliver a bell of a wallop. And there will be a lot of wallops per mile.
