I recently built a 2m groundplane antenna to be installed in my attic. Building an antenna is one thing, but getting it into the attic is another.
This is the lower mounting. Since this is in an attic, there is no need to be overly-worried about strength. There is no wind in the attic!
This is the slot that I used to be able to tighten the mast (which is just 3/4" PVC) to the antenna connector.
Another view of the slot in the mast. Needless to say, this was the one I did SECOND, after I got a little more comfortable with the wannabee-Dremel router attachment.
Side note, after you take a rotary tool with a router blade to a piece of PVC pipe, you will have at least a million of these little shards everywhere.
This is a detail of the coax hole. I drilled an initial 3/8" hole, and then used a 5/16" bit to finish the angle.
And this is the coax hole with coax going through it.
This is the finished mount. I used a hose clamp around the collar to hold the antenna mount to the PL-259 attached to the antenna's SO-239.