#4 is small
I used #4 on the wing tips, they came out great. After 100 hours I've decided to install a second comm antenna under the fuselage. The Bob Archer wingtip comm is marginal, 10 to 15 miles but that's about it. Instead of leaving the antenna and RG400 in the wing I started to remove the wing tip. The paint around the screw heads started to crack slightly. Before removing any more I just wanted to see if #4 100 degree countersunk washer were available. It's not a huge big deal just trying to locate them if nessesary.
McMaster doesn't have the type I'm looking for.
Gary