I have been playing around with mandolin tuners. The advantage is that you get 4 in a nice neat line 25mm apart (about an inch) and the knobs can be flipped left to right without much trouble while most single tuners ned 1 1/4 inch spacing. So how to fit them.

First up I took it apart and drew a freehand copy of the 70s Japanese copy of a 60s Fender headstock. Clamping the backing plate to the front in almost exactly the position I wanted it except it is a little bit to the left of where it should be.  I started the holes using my 5mm brad point bit through the holes the posts go through.

Having accurately centered my holes I remove the backing plate and pull out my 6mm brad point bit and drill all the way through.

Finish everything off, small mention of use of step drill to make the concentric grommet holes, screw together and string up.

Show off the finished product from the front.