Second of two postts for today. See prior post for total time expended.
Still haven't fully determined the Zenith way of mounting the cowl, so may have some rework later on.
Just laying the cowl on top of the engine, it rested not on the fuselage, but a bit up the front of the windshield.
I measured and marked with tape a cut line that would not go too short. Also marked a line matching the rivet line for the firewall. Used a cutoff wheel and trimmed it. Results look good enough to proceed. I think.