"Cecil Moore" wrote
I suspect the half-wave helical wouldn't require as good a
radial system as the standard 1/4WL monopole since the
current maximum point is halfway up the helical.
_______________

Quoting from Antenna Engineering Handbook, 2nd Edition by Johnson and Jasik,
page 13-18: "For a normal-mode helix whose dimensions are small compared to
a wavelength, the current distribution along the helix is approximately
sinusoidal."

John Kraus also assumed sinusoidal current distribution along the helix in
his Fig 8-72 (see clip).

This current sinusoid exists along the aperture of the helix, and not along
the spiral conductor itself. Therefore it is unclear as to the source of
this belief that current would be maximum at the center of "1/2-WL" helix
whose end-end length is 1/4-WL. In reality the current maximum would be at
the base of the radiator, just as it is for a 1/4-wave linear monopole.

The current distribution along the aperture of both of these forms of
radiators has a sinusoidal shape. The current at the top of both of these
radiators must be zero. The portion of a sinusoidal waveform at the
operating frequency, beginning with zero current at the top, that can exist
along the aperture of radiators that are physically short in terms of
wavelength, as in my NEC comparison, appears to be a straight line with zero
current at the top and maximum current at the base of the radiator.

With essentially identical current distribution along the aperture of both
radiator forms, it should be expected that the helix and linear monopoles in
this discussion should have essentially identical radiation resistances and
patterns.

This has been shown to be true in the NEC comparison in the OP, and is
supported by the quoted statements from well-respected authors of antenna
engineering textbooks.