What would you recommend for a wire antenna if there was enough room
for
an 80 dipole? Assume use for 80M , 40M and 20M,
.......................

Myself, I prefer separate dipoles for 80,40,20 fed in parallel with a
single
coax feed. I spread the antennas far apart to minimize coupling.
Why? Pretty much standard dipole performance on each band.
No tuner needed, and thus no tuner losses. Instant band switching.
About as efficient as anything you can run for the bands it's
designed for. Of course, you would need six tie off points, but
those can be trees, fences, whatever.. In the winter I usually
convert my 20m legs to 160m. In that case, it's a 160m "Z"
dipole, and the normal 80 and 40 dipoles fed in parallel. But, so
far this year, I've been lazy and it's still in the summer mode with
80-40-20. The 160 legs have an insulator at the "20m" point, and
I bypass those for 160 with a jumper. I can also set it up to run
on 80m as a turnstile as the 160 legs also have insulators at
the "80m" points. Well...There you have it... MPG will vary... :/
MK