I decided to use Skybolt fasteners along the cowl side joint.
Layout and mark brackets for center, rivet, and center lines.
Mark rivet drill line on cowl.
Position bracket closest to firewall. This bracket was placed such that the centerline of the side joint skybolt fasteners lines up with the corresponding firewall skybolt fastener. It was also placed such that a nominal 3 1/2" spacing was maintained from the firewall fastener. Once position was located, bracket was clamped, drilled, and clecoed.
Layout rivet locations based on 1" spacing using a rivet fan.
Match drill the cowl and brackets at each rivet location, cleco as drilled.