I noticed that Sonex provides nuts to be used on the bolts that secure the brake discs to the wheel. I had originally used the incorrect nuts so I removed each nut and replaced it with the nut supplied by Sonex. Next, I spent some time dry fitting the bearings. This involved fitting the pistons into the half caliper. I used a bit of brake fluid to lubricate the o-ring and the pistons pushed in with a bit of force from my fingers. It was toughest to get the pistons past the initial tapper. Then the pistons when in fairly easily.
With the brakes assembled I fint the wheels and marked the left side for the cotter pin. I then dismantled it all and drilled the cotter pin hole.