#1 Mark fore and aft centerlines on all spars. #2 Do not use actual bolt hardware on spar channels and fittings. #3 Work from front spar aft to back spar , using LE skin for spacing. #13 in and #13 out, use tip skins to align spars at tips. rivet 13 out at front clip then set spar distance and rivet aft clip. #4 use tip skin to set #13 in and rivet front and aft clips. #5 do not set AAPQ 42 rivets in top and bottom of #13 ribs during rib assembly. #6 You need two people to set and align ribs and rib clips