Yes, you are absolutely right.? I'm down with a cold and there is no room left for doing things in my head, lol.? As you say, for constant power to the antenna the voltage will double and the current will halve.? Using I2R the resistive power loss will be cut in half, not 1/8 as I wrote before.
I don't know if it is common to link antenna efficiency to Q, but in this case the equations seem to be the same.? It is the ratio of the inductive reactance to the resistance, as long as the reactance dominates.?
Rick
Rick Collins