Angle of north transept and nave, flying buttress upright

Here to the left you can see the solid flying buttresses against the upper nave, built by Thomas de Cormont c.1240, and to the right the openwork flyers of Renaud de Cormont c.1250. Look at the lower flying buttress on the left--do you see how the upper rim of the flyer continues into the upright and turns a 90-degree corner in order to provide the upper rim for the transept flyer? But the transept flyer, as built, has no use for this upper rim, which is discontinued. The openwork flyers of the transept and choir were intended to serve the functions of both lower and upper nave flyers, supporting the high vaults and bracing the upper wall and roof. The transept flyers are placed somewhat higher than those of the nave. The discontinued upper rim suggests that the builders had originally intended to deploy the more old-fashioned solid flyers around the transept and, probably, the choir