My baffle instructions say to trim the upper baffles to within 3/8 of the upper cowl, but how exactly? I think the standard approach is to take off a little, put cowl on, take cowl off, trim some more, repeat. I've already spent nearly a decade on this thing so I had to find a better way. The pics below show what I did. Get some foam core board from the local office supply and some shish-kebob skewers from the market. Make a mockup of the baffle piece out of the foamboard and trim the top down much lower than the actual part will be. Now jab a whole bunch of the skewers into the foam core and push em down so that only a half inch sticks up. Bolt the foamboard in place, install cowl, and reach in any way you can and pull skewers up until they hit the cowl. You've now got a very nice template for the baffle trimming. I know it sounds pretty goofy, but it worked very well.