There is an offset for the elevator hinge from the top surface of the elevator. My english/metric scale is just the right thickness, so I flipped the elevator on its top surface, put the scale down on the table (photos 1 and 2), and set the hinges from that.
To keep the hing in place I used little rectangles of double sided carpet tape along the hinge and stuck the hinge to the elevator face. Just to make sure the hinge holes stayed aligned, I immediately traced my red Sharpie inside every hole. That way I would know if the hinge shifted at all during handling and drilling. Good thing I did, too, because even with double sided tape the hinge does move a bit. The red circles let me keep it aligned as I worked along the hinge.
After pilot drilling all the hinge holes into BOTH elevators, I then updrilled them all to final size. So the hinge holes are done.
While I was at it I updrilled the bottom surface of the left elevator (photo 3).
My long english/metric scale is the right thickness for the hinge offset; double sided tape going on
Double sided tape holding hinge in place; pilot drilling the hinges into the elevators
Left elevator: all hinge and bottom surface holes updrilled
