The main reason you don't use electric props on glow engines is because they are not designed for the rpm and torque that a glow engine can put out, you risk injury from prop failure.
Right result, wrong reason. An IC engine creates a power pulse every time it fires while an electric motor creates its power smoothly. That's why the props for IC engines have thicker hubs. Keeps'em from flexing and destroying themselves.
Using glow engine props on a electric is safe but the overdesigned prop adds ounces of needless weight to the plane.
Ounces? You'd have to get a pretty big prop to say that, but the idea is sound.
The ultra high powered electric systems that rival glow power and rpm should use glow engine props for the same reason glow engines need them.
Today, 4-stroke engines are spinning 10,000+ rpm and higher in some cases. The power gap has really closed up so I don't think they need special props. Those 4-stroke Rev Ups may be relics of the days when 4-stroke engines had open rocker arms and only revved 8,000 rpm.
Errr, no. Props designed for electric motors, which create more torque than 2c IC, are better for electric motors. You just got through saying the IC props weigh more and now you advocate using them? In the same fashion, 4c engines also create more torque than their 2c brothers, so wider, thinner blades are more efficient. Take a close look at the electric slow flyer props and you can see the extreme of this. I don't about "Rev-ups", but Master Airscrew and other major manufacturers still have the dedicated 4c props.