These results were from Reg's c_poise program. The band is 75 meters and the
coils were about 70 uH. The coils were a relatively large diameter, on the order
of a meter. The wire lengths were about 20 meters. By varying the length the
coil, the coil wire may be varies from 1mm to 12mm.

I haven't tried that program, so don't know what it's for...
But... 70 uh is not far off from the usual inductance
needed to match a 80m mobile antenna. When using
Reg's "vertload" program, which I use for designing mobiles,
I don't see near the spread of coil loss that you see in that
program.
In vertload, to make that large a coil using 12 mm wire,
the coil diameter has to be fairly large just to be able to
fit enough turns in the appx 12 inch height I allowed for
the coil. But when comparing a like coil using 1 mm wire,
and the same coil using 12 mm wire, I only saw about
1 ohm difference, not 5. I'm not sure which is the most
accurate, but so far my real world results in mobile
whips seems to jive pretty well with vertload. I've made
a few coils with pretty thin wire, and had good results
as long as the turn ratio was ok. Ditto for fatter wire coils.
I made one that was 12 gauge and could see only a small
difference from one made with 16 gauge wire. Seemed to
shrink my bandwidth very slightly.
So...Dunno..Would have to do some tests to get the real
lowdown on the differences in loss I guess. But with the
mobiles, I came to the conclusion that real thick wire was not
really needed for a good coil, as long as the winding ratio
was right.
MK