Set the top cowl half in place with a 1/4 inch shim between it and the spinner. Marked the aft end of the cowl for the cutline. Removed the cowl and used a dremel cutoff tool to cut close to the line. Used a long sanding board to sand to the line.
Fit the cowl in place and marked where additional material needed to be removed. Repeated 4 or 5 times for fit