Not much description; just tedious with many holes.
I found out that I was drilling the hinge just fine; I was concerned that I was bending the underlying elevator skin, but after using a fresh bit and patience (!) all worked out well.
Starting from the center of the elevator, drilled thru the pre-drilled holes in the upper skin, thru the undrilled hinge itself, and then thru the lower portion of the skin. Initial holes were all #40. Then updrilled all holes to #30; drilled every other hole to leave a cleco in between for integrity. Removed the remaining #40 clecos and updrilled those holes.
Went over all the open holes with a #20 bit to take them to the final size; cleco'd each hole, then removed the remaining #30 cleco's and up-drilled those holes.