Larry & I chatted about it tonight a bit. Just drilling a second hole further aft as he suggests sure sounds like the easiest solution.

~There's 28mm from the aft side of the hole, to the beginning of the collar.
~If I center a 2nd hole (5/8" = 17mm) within that 28mm space, it leaves 5.5mm on each side.

~The new hole will be about 24mm on center away from the first hole.

~Is that safe enough?

~Can I bias it a few mm's closer to the collar? (wanting to max the space I have to fit the hitch locking pin?)

~Could I make a smaller hole to get it a little closer to the collar? and find a skinnier hitch pin? Or do the shear forces change too much for the worse?