Bed extender questions

I bought a HF bed extender today. When mounted in it's one(!) position in the receiver, it sticks out longer than 4'. I want to alter that to just under 4' which puts the crossbeam at 10' from the front of the bed. This way I can haul 12' lumber with just a flag and I don't need lights on the extender. To do that means drilling a second hole at the blue dot below. The left edge of the tape represents the area that is reinforced inside the main beam with a 1/4 bar stock.



That would be all fine and good, except I also want to be able to haul plywood and drywall using 2x8s on the bed notches and doubled 2x4s on the extender crossbeam. Doing so means only extending the main beam just past the open tailgate. I'd have to run with the spare in the bed because so much of the main beam would be underneath the bed, which is not a thing.



My question is would a third hole for that purpose with no interior reinforcement weaken the main beam when the extender is positioned for the crossbeam at 10'? It would be at the blue dot you see below at 20" from the end of the main beam.



The extender as is is rated for 350 lbs. I could saw off about 2" from the open end of the main beam (the bar stock is only tacked to the main beam there), pull the existing bar stock out, and replace it with longer bar stock adequately past the third hole. I'd have to forget about using the stock first hole position, which is also not a thing because I don't want it anyhow.