In was in and out of the garage today, but managed to get the rear spa doubler counter sunk, and the spar dimpled to match. I started with a practice piece to get my counter sink cage set correctly, and after a little experimenting had it dialed in to where I was happy. With a rivet in the hole, it sits just shy of the lip, by perhaps a couple hundredths of an inch. The reason for the slightly deeper hole is that the dimpled spar needs to sit inside the countersunk hole, which obviously takes up more space than the rivet itself. The challenge is figuring out exactly how deep to go. I’m going to start with what I have, and can always deepen the cut if needed, but I have a feeling it’s right where it needs to be.
As I dimpled the holes and compared to the skin dimpling I did last night, I’m concerned my skin dimples are not crisp enough. The skin is actually quite thick, thicker than the ribs and spar, and I may need more tension in my dimpled to really form the dimple well. I clecoed the top rib to the skin on one side to see how snug the fit was. It’s hard to see in the photo, but there is slight gap between the rib and the skin. There are larger gaps where I fluted the rib, but the worrying area is where the clecos are inserted. 
If I haven’t formed a totally clean dimple, there will be a problem when it’s time to rivet to the ribs, the skin will not sit flush with the ribs, and the skin will develop waves. I decided to adjust my DRDT-2 dimpler and to try redoing a couple of dimples and compare the results. With some more tension, the dimple was definitely crisper, and there was more scuffing of metal around the dimple. At one point I put too much tension in the dimpled, and there was a very slight depression formed where the female die depressed the skin. I adjusted back a little and ended up with what I thought was a good amount of pressure. I kept going, re-dimpling one entire side of the skin. It was very hard to tell the difference besides the scuffing marks. Using the reflection test (seeing how reflected light bends around the dimple), there was no appreciable difference. For both the original and the re-dimpled holes, there is no bending of light until inside the ring around the dimpled hole. I did break out the squeezer and redid the tightest 3 dimples on each side. Continuing to the other side of the skin and redoing all the dimples just doesn’t seem worth it. I think what I have is definitely sufficient, and redoing the dimples is just risking a mistake, and probably enlarging the hole as the dimple sets in a slightly different way the second time. The pics below are of the two sides of the skin, one side has been redinpled, the other hasn’t. But which is which? The second pic is of the redimpled holes. You can see slightly crisper edges
With the dimpling all done, it’s time to prime and then start riveting.
In other news, I am hoping to connect with my tech councilor next week before he heads to Oshkosh. And a letter arrived from Vans with my two missing washers. I added them to the appropriate bag and marked the inventory list, which is now complete.