While doing a prebuy on Friday on an RV-8 I noticed a nut missing from the aft fuel servo mounting stud. This is not the first one of these I have discovered missing on an airplane. I know standard practice has been to use a nut, a lock washer, and washer, but for many years now I have been using AN363 all metal stop nuts with a washer in these locations and I have never seen one come loose. You might consider it on your airplane.
Vic
Vic