Someone gave me a G5RV once and I used it for a couple of years.  I can't
recall what happened to it but something about it fell apart.  I had some
new rotating antennas put up and decided to buy another G5RV but this time,
I added an extra 20 feet to the legs of each antenna from the wire left over
from the old G5RV and put it up about 60 feet.  I think, back in those days,
I was using a KW MFJ tuner; I've had several different tuners over the
years.  I liked the roller inductor type the best, though.  Anyhow, the
added length gave me better band width at the bottom of 80 meters and I
worked a lot of DX with it using my amplifier.  I also got it to tune on 160
meters, through my tuner of course, and it actually worked well on 160
meters.  I found, as is the case with all long antennas, it didn't work as
well on 10 meters because of the multiple wave length of the wire at the
higher frequency.  They become, in other words, somewhat directional, but
they work.  I've lived with, and without, a tuner over the years but when it
comes to antennas like the G5RV, I found that even my internal tuner didn't
work well enough to zero out my SWR on any band.  Of course, it goes without
saying, but I'll say it anyhow, the higher the antenna, the better and this
is especially true with any antenna designed like the G5RV.  Even a vertical
is a compromised antenna but I have used trapped verticals from ground
mounted, to roof mounted, to atop a 55 foot tower and I think I'd buy a
trapped vertical any day, putting it on the roof, before I'd go back to the
G5RV except for 160 and 80 meter operations.  Just one ham's opinion.

Phil.
K0NX