[QUOTE=saturnhr;6828034]
You will never get a perfectly round hole and this will lead to a cracked and/or broken flange due to uneven pressure distribution
Again I disagree; You drill a slightly smaller hole after centering it, and than enlarge it with a small round file and then debur the edges
Again disagree, since the original holes were staggert on both sides, if you drill holes in between on both sides, the new holews will also be staggert.
That will not work. Take a careful look at the holes in the flange. There not a simple straight drilled hole. A precision cut radius is machined on the inside edges of the holes. That requires a special tool which your not going to find in a hardware store. A machinist would simply make that tool, which would be very difficult for anyone not trained in the art of tool making. I spent 6 long and hard months in school hand grinding tools of all sorts to learn that skill. Bicycle hubs are subjected to high levels of stress and if you have even the slightest defect the hub will fail at some point.
You are correct about the staggered holes.