Yeah, I would have loved to actually do the ribs on my RAF FE2b and now on the Bristol F2b. But it is just so expensive, especially if the wing has many of them. Say you add lines for the rib itself, and then two lines close by to each side. That allows the rib to stick up and then then relax down to the original level. I think the new polygon count is (3x + 1) * y where x is the number of ribs and y is the original number of polygons for the wing section without the ribs.
So say a wing had 500 polys to start with and 10 new ribs. The new poly count is roughly (3x10 + 1) * 500 = 15,500 polys.
Executive summary: Your wings better have very few polys to start with if you are going to manually add ribs.