Once the longerons are fitted and all the skins riveted, the fuselage needs levelling and checking for twist. Mine had 0.2 degree twist. By twisting the aftmost bulkhead in the opposite direction, and then clamping the aft deck to the longerons, this was cancelled out to zero before riveting, as the whole fuse then becomes very rigid. I bought a digital level, it is accurate to 0.05 of one degree.
