I'm in the process of countersinking the main spar skin rivet holes on the spar web on a RV-7. The countersink depth is set so a dimpled skin will fit.
In the fuel tank area, there are two rivet holes at each main rib location. This is the same as the leading edge area, except the leading edge area has two rivet holes at every location (one for the bottom skin and one for the top skin).
I can't find a call out for the top rivet hole in the tank area. It seems to me that the rivet hole must be countersunk for a AN426AD3-XX rivet.
Van's couldn't say for sure and will be getting back with me on Monday.
What does the collective say?