How about "gang" drilling the parts? And I might also suggest using a small drill press rather than "eyeballing" a pin vice and bit to get everything square and plumb. Maybe you might build some kind of "jig" to get things straight. These are my old timey ideas, maybe one will work for you.
____________________ It doesn't matter if you win or lose, its' how you rig the game.
Thanks for the tip. I do have a hobby drill press and used that on the Chama coaling tower but, though the holes came out perfectly centered and straight on the beams, they didn't match perfectly on the opposite side. I drilled the holes once the section was assembled. Maybe if I drill the holes before assembly, drilling through both opposite beams while one is on top of the other.
On the Leaverite mine, so far, I did "eyeball" the holes and that was worse than using the drill press.