Riveted the F-721B L to the longeron. This step took some head-scratching and calls to Van's to determine the sequence. In the end, I decided to rivet the secton of F-770 side skin to the longeron, then rivet the F-721B to the longeron. For the tight rivets in the front portion, I used a 4" long 1/2" socket extension as a bucking bar.
F-721B L riveted to longeron
A curious but perfect use of a socket extension as a bucking bar!
