Started riveting doubler plates to the rear spar. Took some time interpreting the instructions on what holes not to rivet, and what holes need countersinking/and or dimpling. On the doubler on the outboard part of the spar, I saw that some guys countersunk .040 thick doubler plate, but I chose to dimple both it and the spar. I countersunk one hole and it just seemed too thin around the hole, the knife edge hole. I think the dimples will be stronger, although I'm sure countersinking them would have been fine.
