Redrilled and countersunk the glassed-in holes on the L nostril. Trimmed cowling exit to provide more exhaust pipe clearance. Started oil door construction— using an Avery hidden hinge, and an RV-6 composite oil door, trimmed to fit. Plan on using one or two Camloc KM610 button latches. Can't reuse the metal door provided because of the extra holes, but the backing plate I can reverse and use for the flange. On my RV-9A I used one Camloc, but it popped open in flight once until I tweaked the strikeplate. On my Rocket, I used two with no problems— but the door doesn't have any internal pressure because of a plenum doghouse. I will go with two on the S-21, since it will have internal pressure and to keep the fiberglass door flush. I will put a stiffener on the fiberglass.