Today I mounted the lower cowl to the firewall and trimmed the top edges.
With the lower cowl in place on the fuselage and strapped to the upper cowl I drilled the pilot holes for the Skybolt grommets using cleco grommets as drill guides at each Skybolt flange while reaching through the oil door hole. I did this for the top four Skybolt locations on the right side of the aft edge of the lower cowl. With those four holes clecoed I removed the upper cowl to access the Skybolt flanges on the RH side. Clamped the top aft edge of the lower cowl to the Skybolt flange and drilled the top four holes on the RH side.
Opened up the holes to 15/32" with a step drill.
Removed the lower cowl and installed Skybolt grommets and studs. Riveted Skybolt retainers to the Skybolt flanges that correspond to the holes I just drilled.
Reinstalled the cowl and fastened the Skybolts. Drilled the remaining holes and installed Skybolts.
Installed the upper cowl with its sides overlapping the lower cowl. Drew a lines on each side of the lower cowl corresponding with edges of the upper cowl.