I used a loop of rope to bring the bottom cowl up against the upper cowl. Once I had checked every part of the fit several times, I started the trimming.
It takes many, many cycles of on and off to get everything trimmed to size and fit up. I made a few minor errors in the trim that will need some attention to correct. I already had the exhaust on and had to trim around the expected locations before I could even put the cowl into place. I trimmed to deep, so will need to fill in those spots.