Ed_G wrote:
My expertise is weak in this area, but just guessing.... using twin
coax in the above configuration, if the shields were grounded, would
allow the feedline between the antenna coupler and the feedpoint to be
'balanced' and yet the shields would not radiate as they would with a
single coax run.

Side-by-side runs of RG-11 (Z0=150 ohms) would reduce
the SWR on the coax and change the impedance seen by
the tuner from 0.3-j69 ohms to 1.9-j154 ohms which is
quite an improvement. You can increase that feedpoint
impedance even more to 2.5-j170 ohms by using side-by-
side runs of RG-133 (Z0=190 ohms) if you can find it.
--
73, Cecil http://www.w5dxp.com