I thought I saw a difference on 20 between the Nott and the Tarheel so I did
it again:

System: ball mount on Dodge Durango right rear.
I'm inside with an MFJ analyzer and about a foot of coax direct to the
antenna.
No matching network. Tune to resonance (X=0).

Today's measurements:
At resonance on 20 meters the Nott is 20 ohms and the Tarheel is 31 ohms.
Maybe copper vs aluminum does matter.
H.

73
NQ5H