It's hard to see in the pictures, but there were a bunch of rivets to drill out. When I had bucked the rivets hidden by the spar, I had held the bucking bar at a slight slant. This made the top of the rivet slightly slanted. So, I drilled them out and replaced them.
When I riveted them back in place, I used a bucking bar helper. I taped a small piece of wood on one side of the bucking bar to help hold it perpendicular to the rivet. The wood rests on the spar holding the bar at the correct angle. Also, I was able to squeeze quite a few of the rivets through the opendings in the leading edge.
