This is easy to misunderstand. The reason they say when running a glow fuel with 65% alcohol one should use a cold plug is because a fuel with only 65% alcohol would have a nitro content of anywhere from 15 to 30% depending on what the oil content the fuel has. With higher nitro, one uses a colder plug. It really doesn't relate to the alcohol percentage; it relates to the nitro percentage.

Engines running FAI fuel, which is 80% alcohol and 20% oil run hotter plugs than ones running nitro. The determining factors are the compression ratio, nitro content, atmospheric conditions, etc. for choosing a glow plug. Generally, these engines running Gas/Glow respond well to a hotter plug such as the OS four stroke plug.

When removing the glow plug power, if the engine drops in rpms, it could use either a higher compression ratio, more nitro, or a hotter plug.

AV8TOR