Made a couple of clamp-down blocks for the front spar to prevent fore-aft movement.
Positioned the skin on the frame and match drilled the rear spar starting at the CL and working outward.
Tip: At a few locations it was necessary to move the spar outward slightly to get proper alignment so I created a puller tool from a strip of 0.040" with a tight, short acute bend on one end. Also found a pick tool that worked great for moving rib flanges into position.
Aligning and drilling of the ribs and front spar required only minor adjustments to get the rivet lines to fall perfectly under the pilot holes although setting up these adjustments added quite a bit of time to the process.
Brainstorming methods for laying out and drilling the top before riveting the bottom - just like the pre-punched skin from ZAC. If I can identify the center of the nose bend then the measurement from the lower front spar to that line would be the same as the measurment from the line to the top of the front spar. From there it's just a mirror layout of the bottom