Four of the problem rivets are where the hinge brackets and stiffener rivet heads get in the way. As you can see here, it's nearly impossible to squeeze the shop heads of these skin-to-spar rivets with conventional yokes. I ordered a special no-hole, no-die narrow-head squeezer yoke for this purpose.
UPDATE: the thin-nose, no-hole yoke did not solve the problem. It, too had clearance problems. So here's what I had to do...I had to grind down the tip of my regular yoke as seen in the following picture. That allowed me to get a bit closer to the rivets and it did the trick. Word from the wise...if you're not yet to this point, just save yourself the hassle and put the spar rivets' machine heads on the outside. That will alleviate this interference issue.
The fifth problem rivet is the top right rivet (closest to the leading edge). My conventional squeezer yokes don't have enough clearance to get in there. I got one of those leading rivets, but with that one in there it's impossible to get the other one. With the new yoke it'll be no sweat. (By the way, don't let the "waviness" in the rib flange sway you...that's just "fluting" and it's intentional...you flute the rib flanges to make sure the ribs are straight.)
I cut out the V-groove templates and measured out their position on the workbench, and I screwed them into place. They're ready for use.
I started working on the bending tool (a couple 2x8s hinged together) but my first version (which only used 2x6s and was hinged too tightly together) was a failure. I've gotta get 2x8s and leave about 1/8" gap between the studs to facilitate a nice, clean bend. More on this next week.