I realized today that I didn't install the transponder. I went back and looked at the instructions which said to install the backplate must missed AND THE TRANSPONDER. So took the top skin off again and did that (and discovered a screw on the backplate I hadn't tightened). But in the process of moving the big cables around, those ProSealed grommets are still coming out of the hole. I really hate the split grommet method Van's uses. I'll have to research more but I'll probably have to put ProSeal on the interior side.

The instructions seem to show the top skin being off for the installation of the PFD (the GDU 460) so I took it off -- again!! -- and started putting the screws in but there's nothing to hold the top left screw. So I asked Van's support and got my "duh" moment when Eric reminded me that I'd added a single lug nutplate (you know, the ones that took three weeks to get?) to the top skin frame. But when I took the top skin off, of course the platenut in that spot disappears. Like I said, "Duh!" I feel like my cognitive skills were better when I started this project.

Anyway, I also installed the radio.

I'm trying to keep things from looking like a rat's nest back there but I'm not sure I'm succeeding.
Now, then, for the problem.

While removing screws in the panel skin -- a boring task -- I just sort of gazed around taking stock of things when I noticed that there are 4 open rivet holes in the center spar carry-through under the fuel tank. No clue how that happened. So I'll have to remove the fuel tank and squeeze those.

I don't know how I missed it but I went back to the plans (20iS-U_12iS page 5 & 6) and these require AN470AD4-8 rivets. I must've gotten distracted. Bad thing.

(Update: Went back and looked at the builder log entry for 12/12/17 and I had noted that I couldn't finish four rivets because they were in a big that was backordered from my fuselage shipment. There's no way those rivets are going to be around anywhere now so I'll have to order some more)