I decided to order new Z brackets for both tanks. Looking up through the spar holes, this Z bracket is well aligned...

...but down here at the inboard end of the tank, the holes are off. This is because the baffle was flexed when I back drilled these through the spar. $22 later and Van's has 14 new Z brackets headed my way.

Working on getting the right wing level / plumb / square. Here, the outboard end of the spar is nice and level.

I made more wedge blocks for the inboard end of the spar.

I needed some more C clamps before I could level up the inboard end of the wing, so I switched to countersinking all of the platenut attach holes on the right joint plate.

The pictures up above are from very early in the morning (i.e. ~3:00 am). Here we're picking up after work. I had a chance to stop at Home Depot to get two more C clamps. After tweaking with the wedges and the supports, the spar is nice and straight.

A good fit!