The next thing you do is attach the nutplates on the bottom of the spar that will help attach the inspection plates to the underside of the wing. In this picture these nutplates are the three on top.

There are three inspection plates under the wing that you can unscrew to take a look around periodically. These are attached to the spar with #6 screws instead of the #8 screw nutplates I was working with earlier.

You guessed it, more nutplates. You are looking at the aft side of the right spar. I have countersunk the rivet holes so that the rivets will sit flush with the spar doubler plate. Later on in assembly there will be a block of aluminum that will sit up against these rivet holes, so they need to be flush.
Here is the other side of the spar and the nutplates. Notice that these rivets are quite a bit inboard from the edge of the spar. I had to use my 4" yoke to reach these, but it was a snap. It pays to invest in a variety of yokes to make your life easier.