In the case of using a mechanical and an electronic vario - capacity
and no capacity respectively - and a glider in which the tubing aft of
the panel is not that accessible, I wonder whether just teeing and
having a 7 foot length of tubing to the vario would isolate the TE
line enough to minimize mutual interference. I accept that this would
add volume to the system, which may be a problem, and that the handful
of tubing might be a problem for space behind the panel.

Would this be a workable solution?