Started the day by using a centre punch to tap the threads of the studs and nuts. This is to prevent them from unscrewing. There's very little load on the nuts themselves other than to prevent the studs from backing out of the spar.
I then measured and marked out the locations for the ribs. As luck would have it, a couple of the ribs need to be moved a slight amount. One rib would have been located in the centre of one of the spar mounting studs, and a second rib would have been located in the centre of one of the landing gear mounting bolts. Not a big issue, both ribs will be relocated about 3/4" outboard. Test fitting the ribs onto the spar. A couple of the ribs had to have the gap in their shear webbing opened up to fit the width of the spar. The root rib need to be cut into two parts; a section forward of the spar and a section aft of the spar. It is drawn and built as a single piece but it can't slide down the length of the spar from the outboard end as it doesn't have enough clearance for the studs and nuts. It can't be mounted from the inboard side either because the spar attach plate has two "ears" on it that the wing attach bolts go through. These ears are taller than the spar is deep. Additionally the spar end plate extends forward of the spar by a couple of inches. So after a bunch of fiddling and trying to fit it one way or another, I realized that the best way would be to cut the root rib into two. I cut the rib's upper and lower stringers at a shallow angle such that the joint will be a nice scarf joint.