I have a mis-formed lower cowl and was having trouble getting things even remotely to fit. I had some down time in LAX so I went down to TOA to see what I could learn. I talked to the man that puts on the cowls for the Sling assist build there. He showed me a jig he made and the process and steps they are using there. It's a bit different from the manual. I made my jig and started as instructed by TOA. Mark a centering line on the aircraft on the upper fuselage by the firewall. Rotate the prop hub to create a level center on the spinner. Put the jig in 2 spinner screws. The jig has adjustable jam nuts to set the vertical and the jig mounting holes are elongated for horizontal fore/aft. Drill #30 and put clecos to set (to be filled later). I attached the bottom cowl to check fit and luckily the offending side just barely fit. Now that the upper cowl is fixed and will be the reference for the bottom cowl after the edge is trimmed and cam-locks installed.