Wish I had taken pictures, but:
- Take four paint stirring sticks.
- Clamp them on the outside of the sides of the lower cowl near the four corners so that six inches or so of the stick is above the lower cowl edge. Location is not critical, just in a straighter area so you can clamp easier.
- Clamp the top cowl on the sticks leaving four inches or so gap between the upper and lower cowl (sticks are on the outside of the cowl halves). Make sure the firewall edge of the cowls are lined up, i.e. top cowl is not forward or aft of the bottom cowl.
- Adjust the clamps until the gap is exactly the same on all four sticks. The top cowl is now parallel to and "floating" above the lower cowl. (consider the thickness of your forearm in selecting the gap dimension!)
- Take another (thinner) stick and tape a sharpie to it with the marking tip sticking out about 1/8" or so from the stick (stick and sharpie form an "L"). A dowel works fine.
- Trim the stick so the distance from the top of the stick to the sharpie tip is the same as the gap between the cowls, plus your desired cowl to baffles clearance distance (1/2" or so) <<< important step!
- Reach in through the gap between the two cowls (created in step 3) and run the marking stick along the baffles while touching the inner surface of the top cowl (while keeping the marking stick vertical)
- Draw all around the outside of the baffles
You have just drawn the exact trim line for your baffles. ...