(page 21-10) Double flush?.........              

Forget the commode jokes.  The bearing bracket for the control columns requires that the rivets holding together the plates which sandwich the bearing be squeezed "double flush."  I had no idea how to accomplish this, and, in fact, had never heard this term before.  It's pretty easy to imagine what it means -- nothing should protrude from either side of the rivet hole.  Beyond the rather descriptive name, the build manual offers no clue.  Homebuilt Help video to the rescue.  Turns out you countersink each side of the hole, then squeeze the bejesus out of the rivet.  The shop head sort of conforms to the cone-shaped countersink (red arrow in the pic), but still protrudes a bit.  Apparently this is OK.  I don't know yet what part needs clearance here.  As usual, all will be revealed later in the build.

All the riveting beneath the seat floor and baggage compartment floor seemed to go well for the most part.  One particular nutplate, however, required squeezed rivets I couldn't reach (red arrow in the pic -- the rivet is below the horizontal flanges with the already-squeezed rivets).  The "no hole" extended reach, close quarters arbor for my Main Squeeze from Cleveland Aircraft Tool saved the day.  Pricey, but only way to do the job ($120 for the arbor alone).  Airplane buildin' ain't cheap.  I'm figuring I'll have at least $70k in this mofo before it slips the surly bonds of earth sometime in 2014.