Very nice construction and a good idea, and I'm glad you used an N connector instead of an SO-239 for prevent water from getting into your coax. One thing I can never figure out is why do so many people gravitate to copper for VHF/UHF antennas? I used copper to build a 6m 5/8 wave ground plane for my ham station at work 30 years ago. The only reason I used copper was because it was free and, of course, soldering is easy and makes a permanent weather seal.
Many years ago, I made a 2m J-pole using 1/4" aluminum rod. Easily made and adjustable. Of course, 3/16th or 1/4" rod would be a better choice for UHF than 1/2" or 3/4" copper pipe, which is 5/8" and 7/8" OD respectively, as it wouldn't so broad-banded reducing what little gain you would have with a perfectly built J-pole.