Anyone have an idea how much of a typical GA prop's drag is due to induced drag? The tips are generally at some high fraction of Mach, that makes for a lot of parasite drag. I'd bet a nickel that, in typical climb or cruise, induced drag on the prop is a small fraction of all forms of parasite drag. Skin friction, the burble on the back side of that airfoil, turbulence due to uneven linear speeds/ pressures along the blade's length, etc. The drag we see in typical airfoil plots of Cl/Cd assumes an airfoil of unlimited span (no tip vortices), so that's all parasite drag, it ain't induced drag. A square test club has no induced drag at all (makes no lift), yet it effectively absorbs every bit of HP the engine can produce. Sure, a square test club is draggy, but it also absorbs the HP used by a real prop to do real work in producing thrust (that's where about 70-80% of the HP goes, after all).

We know that in many cases, a two-blade prop outperforms a prop with more blades. There are many other factors to work into the mix, and I suspect fixating on induced drag won't yield results that match what we see in the real world.