Used string method to check spar for straightness on bench. Measured, drilled & clecoed 7v6-3 (rear channel angle) to rear channel & rib # 3. Measured, trimmed & fit r-channelbetween ribs # 4&5, drilled & clecoed. Drilled relief holes on piece of channel & bent flange to 25mm for (between ribs #5&6)