Bob (WA6EZV) did some more work on his TRO-2.  His first attempt (before we settled on the thin-wall sewer pipe), was in a Schedule 40 end cap.  A piece of Sch40 pipe fits into the large endcap (seen here with SO-259s).  The wall thickness of Schedule 40 is about the same as the end cap wall (left side of photo).  The sewer pipe is just a thin shell (right side of photo):

His latest innovation is to put the batteries next to the PCB, rather than above or below it, so the pipe can be shorter.  He has little aluminum binder posts as extensions:

More photos here.