Knowing the size of the heads and cylinders, work began on the general of the layout of the engine. The goal was to make the engine as small as possible. This meant a narrow V angle and short length.
Since the engine would have a flat plan crank, the V angle was open to dimension restrictions only. Inertial calculations were done to confirm that the first order vibration was not too different that the 4 cylinder engine (without the counter rotation shaft).
V angles down to 60 degrees were considered, but it quickly was recognized that the separate cylinders and straight intake tracks would eliminate very narrow angles. The decision was really between 75 and 72 degrees. It was decided that 72 degree was too narrow because the metal in the top of the case between the cylinder banks was quickly disappearing as the V got smaller, not leaving much left to hold the top of the case together. A central oil galley is the most compact way to go and it would have been problematic with a 72 deg. angle. So 75 degrees it was going to be.
This proved to be a good decision as the top of the V in the case ended up being very tight with the cylinder skirts, oil jets and crank counter weight all in very close proximity.