I have been playing with PVC and Aluminum Tubing
for building rigid dipoles.
Most have been built for 10M, 6M and 2M.
With the idea of portable operation.
There is a picture of a center "T" with BNC
from one of these smaller antennas.
There are also a number of pictures of a 20M dipole here.
For this antenna, a coax "pig-tail" was connected
to the interior bolts on the center T.
You will note the larger hole. This is so that a metal nut can
tighten the assembly at this point
while providing a good physical and electrical connection to the antenna.
It is full-size, no loading. The antenna
is in operation at the QTH of KB0HNR.
It is a top his 45ft tower.
Much to my surprise it has weathered severe
storms with winds in excess of 60mph.
I hope that these pictures will help
you in your construction projects.