I guess my previous post answering this got lost in the updates. 2" PVC is 2" ID, about 2 1/2" OD. Kitfox spars are 2 1/2' OD, with .065" wall thickness, so Spar ID is about 2 3/8" Then you have the doublers where the wing pins go though the butt end of the wing spars so that reduces it further. Spar spacing is 27 1/2" center to center. JImChuk