Reg, G4FGQ wrote:
"Changing the current distribution and changing the effective height are
one and the same thing."

Could be. Antennas are reciprocal. A common definition of "effective
height" for receiving antennas is simply the ratio of volts out of the
antenna versus the field volts per meter acting upon the antenna.
Constants provide effective height in feet, meters, or in the units of
your choice.

Best regards, Richard Harrison, KB5WZI