Excellent idea with the paper clips.
Here is a method that worked for me. Before I did any trimming I secured (duct tape ?etc?) the top cowl in it's correct position above the bottom cowl so that there was an even gap on both sides between the cowls (cowls parallel to each other). Measure this gap and add the required clearance. For example, if the gap is 3? and the clearance is 3/8? the total is 3 3/8?. Make up a spacer to this length (I used a popsicle stick). Remove the bottom cowl. Now reach in and holding the spacer vertical against the baffle and touching the secured top cowl, use your felt pen to mark the baffles for trimming all around. You should now have a line on the baffles that is 3 3/8' (for example) vertically below the lower surface of the top cowl all around. If you feel really brave then start cutting on the line. I suggest trimming maybe 1/8 or 1/4" above the line and see how it looks. You could use the paper clip method now to check the clearance.
Warning. This worked for me, it may not work for you. Don?t blame me if you have to get new baffles because you cut your old ones down too much.
Fin
9A Australia