John,

The Moxon is a beam that relies on the element end gap to set up the
feed impedance and directional properties. You basically need to
mechanically scale the whole array, width, depth, and gap in order to
keep it working like a Moxon.

The SteppIR curved dipole thing that goes down to 40m is just an end
loaded dipole that uses a transmission line stub as the loading.

It's just a regular dipole until the element goes around the curve,
then the doubling back adds a transmission line stub to the ends of the
dipole, bringing it to resonance at a lower frequency. I tried it in
EZNEC.

This would be a fairly buildable antenna except for the sliding
contacts at the feedpoint.

Dan