What is the downside of the French method of placing two twin mountings inside one quadruple turret?
Short answerThe main stated disadvantage is extra weight from the two sets of trunnions.
NotesTwo twin mountings sharing one turret enclosure are criticised for their weight. When the exchange resumes after a signal interruption, the two sets of trunnions are specified as the reason. No separate tactical penalty or quantified weight comparison is developed.