John
Your definitely not shy when it comes to engineering projects and I admire your courageous approach to tackling difficult problems!
A word of warning, don't let health and safety see the picture of that oversized drill bit stuck in a small chuck, it's bad enough if you're just using it for countersinking but if you're drilling holes that size open it up with smaller drill increments at a very
Low speed, until your just clearing the final hole, the alternative Gung Ho approach could have everything flying around the room ( including yourself)
Do you have a wood stove handy?
I believe a certain forum member has a supply of firewood to burn that just may have the hole positions your looking for!
The guitar looks great but did you just buy it to match your kitchen mugs, or have you got them colour coordinated for the steel?

Looking forward to seeing and hearing the finished product sometime in the new TEIR or 2021 whatever comes in first!
All the very best to you and yours
Robert