In my ASH-26E, the ELT is located by my left elbow, and the entenna is
the wire whip installed in the baggage area above the spar, as the is
the only non-carbon skinned part of the glider.

I didn't bother with a ground plane as I figure amny chrashed airplanes
also may not have a ground plane to work with...

The antenna is mounted to an aluminum bracket behind my left shoulder,
and curves around the inside of the baggage area toward the rear and
right side. Springiness keeps it nicely pressed against the top of the
fuselage.

As for transponder, I had the factory install it, as the cost was
essentially parts - something like $120 four years ago. I still
haven't installed the transponder itself, but am running the antenna
through a regimen of abuse as it occasionally catches on the trailer.
The antenna is installed through the fuselage just aft of the wheel,
and there is no added ground plane, as I assume the carbon skin is good
enough.

-Tom