Drilled holes for mounting nut plates to left wing tip. Counter sunk holes for #3 rivets. Counter sunk center nut plate holes to accept #6 screw dimple. Riveted all of the nut plates into the wing tip. Started fitting the tip rib into the back of the wing tip. Stopped to wait for clarification from Van's builder's assistance regarding the orientation of the rib - flanges inside the tip with a flat face or flanges towards the wing with about a 5/8" recess.
Heard back from Sterling Langrell of Van's at the end of the day that the plans call for the flanges to point into the wing tip, but that they can be reversed which makes installation easier. However, to reverse them requires using the opposite rib in the wing tip (e.g. left rib in the right wing). Since I have already drilled and fitted the right wing tip with the rib flanges pointing into the wing tip (per the drawings), I will stay with that installation for both wing tips and deal with the more difficult riveting.