Riveted inside corners with 410 rivets to bulkhead # 6-5-4-3 on bottom and 6-5-4 on top. Waiting for dimpler to complete stringers. Just relized that the two lower inside corners need to extend past the #2 bulkhead, this information is not clear in the instructions and is easy to miss. Not sure how far it extends beond the #2 bulkhead either.