Bill,
Not all 'auto-tuners' are built equally. Meaning that
the '850's tuner may or may not work with balanced feed
line. (I have two radios with auto tuners, neither will
handle the balanced feed line, even using a balun. One of
them is an '850', best radio Kenwood ever made!). It
depends on what the range of impedances the tuner is able
to handle, and what the antenna system presents to it. It's
certainly possible, but I wouldn't count on it. If money were
no object, and if I had the required building skills, I'd
have a 'balanced tuner' that would handle anything I could hook
to it. But! My 'lazy' out weighs my desire, and to be honest,
I can't tell the difference in not using a balanced tuner. (My
loop isn't anything near 'optimum' in where it is and how high
it is, by the way, so using a balanced tuner just isn't going
to make much difference. It does what I ask of it, so who
cares.)
'Doc

PS - There are only two kinds of people who use feed lines in/on
the ground. Those who have run over it with a lawn mower, and
those who will run over it with a lawn mower...