RE: Regarding SP series engines, props and airspeed...
I only have the 4-blade hub, and it'll be hidden inside a P51 spinner so as not to be seen so it's scaleness is irrelevant to me as long as it fits and does the job. I don't know anything about the 3 blade hub, if I get a Top Flite Corsair ARF later this year (presuming my Mustang project turns out well) then I may get Vario's 3-blade hub for that plane.
- Michael