Have you got photos or a snapshot of the relevant drawing to show exactly which ones?
If they're the ones I'm thinking, you mean the two inner nose ribs that are canted in at a bit of an angle to match the skin? From memory these were really hard to fit in place and buck as I think there's 3 or 4 pieces stacked up here to rivet, and the angle makes it hard to get a clean shot with the rivet gun. Also made it impossible to get a squeezer onto it as I recall.
You'll need to use an offset rivet set, and a thin bucking bar (like the tungsten one with an angle on one end). I often found it was helpful when setting -4 rivets in big stack-ups to use a 1/8" punch in an adjacent hole and wiggle everything around so the rivet I was trying to set would go in nicely. I also found it was good to try to actually get all the rivets into the holes before bucking the first one just in case things move a little and the subsequent rivets become a problem.
Keep at it, I just checked photos of my build and those particular rivets look good in the photos so I must've somehow got them in and bucked OK.
RV-9, Empennage and Wings about done, Fuselage started.