I got my wings secondhand and the countersinking & riveting in the wingwalks area looked pretty bad. I ordered new upper inboard skins and wingwalks doublers and dimpled the ribs, doublers, and skins. Looks beautiful now (BTW this is also how I did my RV-8 wingwalks almost 20 years ago). I don't understand why Vans tells you to countersink this area...It's harder to get good results and as Carl mentioned results in a weaker joint compared to dimpling. I also highly recommend dimpling the aft baffle -to- tank skin rivets...I've previously posted about that area.