What diametric ratio must a fractional wave length radiator be to
allow contrary current flow thru it's center. ?
Diameter / wavelength = 1.0, 0.5, 0.1. 0.001, 0.0001,
0.00001,...?
Regards
Art

That depends on your return on investment in cost and labor, and the
application. Since the skin effect applies, thankfully, the flow through
the center is less of an issue.

Should we use tubular elements?

Or as some have done, use Silver or Copper plated steel wire or rod? At
some frequencies, this is profitable.

Why should we "allow contrary current flow through it's center." as opposed
to promoting the skin effect, since current flow through the center does not
radiate? Like eddy currents in a transformer are just loss.