Deburred all 4 brackets and attached the nut plates. The smaller brackets got dimpled and the larger brackets got countersunk...probably due to the angle of the flange would prevent dimpling and squeezing the rivet. I went ahead and clecoed everything together, but quickly realized it would be easier if I rivet it together in steps. First rivet both crotch brackets to the rib with the mixer, then second step, rivet the remaining rib the crotch brackets...worked out great. I had to use the hand squeezer for step 1 and the pneumatic puller for step 2.
