Mike S. and I really made some headway this evening. The HS-404 and HS-405 ribs are drilled for fit along with the HS-710 and HS-714 re-inforcements. The skin (and it's computerized holes) are used here to align the spars and ribs for fit and drilling. The parts fit together well -- it's hard to imagine how much more time-consuming it must be to locate, align and drill all the holes without the benefit of this computerized, machined-holed kit! I must say, that in this case technology has really benefited the consumer. There is only a little bit more work on the left HS before moving on to do the same for the right HS.