This picture shows the lightening that I did to the underside of the wing. I cut thru the obechi wing sheeting and removing panels of the sheeting. Then I removed the foam from the outer most panels down to top wing sheeting. I would not remove any more panels of the foam, it effects the torsional stiffness of the wing. I am going to recover the bottom of the wing with iron on covering.
This seemed to make an enormous difference in the wieght of the wing, without dramatically effecting the stiffness of the wing or torsional twisting of the wing.