I finally re-installed the cowling to check the clearance between the cowl front face and the prop spinner. I had exactly 1/8" along the top and bottom, but only 1/16" at the 3 and 9 oclock positions where the top and bottom cowling flanges come together...not enough.
To fix it, I built up the areas on the cowling behind where the top and bottom flanges come together, then sanded the cowlings' front faces at the 3 and 9 oclock areas. This gave a nice flat face. With the cowlings back on, I rechecked the spacing...perfect 1/8".
Spinner clearance at the cowling flanges...too tight
