Ian Jackson wrote:
"Maybe 377 ohms?"

Arnold B. Bailey in "TV and Other Receiving Antennas" shows his
calculations of radiation resistance at the current maximum point for a
center-fed thin dipole at its various resonances:

1st--------------------------------72 ohms
2nd------------------------------200 ohms
3rd-------------------------------102 ohms
4th-------------------------------260 ohms
5th-------------------------------117 ohms
6th-------------------------------295 ohms
7th-------------------------------127 ohms
8th-------------------------------321 ohms
9th-------------------------------135 ohms
10th-----------------------------340 ohms

He also shows the current distributions and feed point resistances which
I can`t and won`t.

The input resistance of the center-fed antenna at resonance never equals
the surge resistance in value, but is related to it.

Best regards, Richard Harrison, KB5WZI