Hey Plumber,
I have an L-4 as well and this worked very well: Use a 4-40 screw and blind nut behind sidewall or use a threaded insert instead of the blind nut if getting behind the firewall is too difficult. Cut a piece of brass tubing about 3/8"-1/2" that you can force thread the 4-40 into. Cut the heads of the screws off (use a dremel wheel or the like) and screw the brass tubing into the cut end allowing 1/8"-3/16" from the end of the screw to the top of the tube. Drop some solder into the hole and top it off flush. Drill a tiny hole through the brass about 1/16" from the end and push your "Jezus" clip through it. DONE. Now you can unscrew the thing without removing the clip and use the clip as a gripping surface to tighten the screw down. Use a small metal washer and small "O" ring (the Sullivan "O" rings for their fuel fittings work very well) between the washer and the cowl. This will protect the cowl and produce enough tension to keep it from unscrewing itself in flight. Oh, and balance your prop. Its alot of work but you can't beat the look.