Had to break down the crates to put out in the trash and decided to go ahead and salvage some of the lumber to build the leading edge cradles.
Cut the stringers to length and cut rectangular panels from the plywood. Used leading edge rib as template with about 3/16 extra. Cut them on the band saw and then clamped together and did my best to sand matching pairs. Got them all screwed together and they came out really good.
Will add a little weatherstripping to finish them off.