So here's the process of drilling all of those wonderful holes. I clamp off 3 holes at a time, alternating top to bottom and beginning in the middle and moving first left and then right. The hole locations get an application of liquid Boelube...great stuff to keep bits sharp and to make the holes drill faster. Then a #40 pilot hole is drilled. Finally the hole is enlarged to #21 for the rivets to fit. Yup, gloves are handy when it's 4 degrees F out side and the shop only heats up to 58. (I'm cheap, I could heat it to 80 but I gotta save money for more metal!)