I'm using only the three screws and have had no problems whatsoever. I drilled 1/8" holes in the cowl and inserted black rubber grommets in each hole. I use a #6 flat washer on each screw to keep the head from pulling through the grommet. After drilling into the hard points on the fuse, I threaded the screws in and then took them out and hardened each threaded hole with a half dozen drops of thin CA. Works great and haven't had anything come loose in many flights. If you're going to be running a high vibration engine, you might want more fasteners.