>>1752450It's a matter of propeller optimization, really. The loss in terms of drag from the pug nose was more than compensated by the increase in propeller propulsive efficiency you get by making the spinner smaller, especially because you are using a two bladed propeller with little interference between the blades.
You only need bigger spinners at higher speeds, as the limiting factor to efficiency goes from thrust to area to propeller tip speed.
Fun fact, compare the spinner/cooling area that "rare bear" ended up for it's world record with the arrangement in the deperdussin
>>1751066. Ahead of it's time, indeed.
