It seems the natural tendency is for the bottom cowl to play outward a bit, which makes it more challenging to ensure the top and bottom cowl are trimmed properly relative to where they meet at the split line.
For some reason, the right side seems to be cooperating much more than the left.
Continued the process of identifying conflicts, marking, sanding and repeating. Generally in a 2 hour session, I can remove the cowl halves and sand then re-try 2 - 3 times at most. I am being conservative because I don't want to remove too much.