Designs begun in 1930 would probably inherit F3's all-forward arrangement and then improve its armor and machinery. Retaining two shafts could preserve hull and hydrodynamic advantages if the system worked. Four shafts would give greater redundancy because a casualty could leave several independent lines of propulsion available. Three shafts offered an awkward compromise because the centerline shaft tended to create problems, making propulsion layout a real design choice rather than an incidental detail.
Notable Point · 1:19:49-1:21:13
Two shafts favored efficiency, while four offered redundancy
An F3-derived generation would force a choice between two-shaft hydrodynamic efficiency and four-shaft damage tolerance, while three shafts offered a troublesome compromise.