Prepped the left and right seat floors and shot them with primer. Drilled the #40 holes for nutplate attachment of the forward mounting holes which secure the F445 flap blocks. Machine countersunk the holes using a 90 degree angle drill with a mini countersink attachment. Worked pretty well. Used some CCR-264SS-3-2 (cherry 3/32” countersunk) blind rivets to secure the nutplates.