Excuse me for butting in but it seems to me that what we are talking about here is a truss. The whole purpose of the webbing is to keep the top and bottom spars apart. In order for the wing to bend the spars must collapse together, if they can not do this because of the shear webbing then the tensile strength of the spars comes into effect. In other words the spars would have to break. The ribs alone are not strong enough to keep the spars apart because the grain is horizontal, so adding more horizontal grained webs is not going to help much.
It is easy to prove this point. Take two sticks of equal length and put them together side by side then bend them both together and observe what happens to the length. The one on the outside of the curve having a longer circumference to cover will end up shorter. Now hold them apart a little and attempt to bend them keeping the ends at equal length. At some point they will have to come together because the inside one will have to form itself to a smaller radious.