Ok, It's done! There were a few issues, but overall and it looks great and sounds *awesome*
Lessons learned:
1. Practice on scrap wood first. If the armboard is ply, use that. If it is solid wood, use that (practicing on a piece of scrap wood that is the *same* as the armboard is key here...).
2. Mark the armboard holes and drill first in order to be able to screw the board down to another board.
3. Use a drill with enough torque and power to go through the tonearm board wood.
4. Feel free to use the dining room table as a workbench, but only if the wife is out of town (woo-hoo!)
Solid Cherry needs a drill with more torque than my cheapie 18v drill could give it. This caused it to seize up every couple of turns, which lengthened the drilling time, and ultimately cause a slight splinter on the face (completely covered by the tonearm base, thankfully). In hindsight, I should have scored the circle with an Xacto knife as
@biscuithead suggested. I think this would have solved the splintering issue (well, that and a higher powered drill)...
Onward and upward.
Practice drills :
It fits! (washer goes underneath, but you get the idea...)
Clamp board and indicate edge (Happy wife, happy life...).
Mark and drill armboard holes, screw board down tight:
And here's the final product: