<The screw-on elements are subject to coming lose with vibration, so one would need a way to permanently tighten them (lock-tite on threads?).> Replace the steel threaded rods with stainless steel threaded rod or studs. Available from local hardware store or McMaster Carr. If you want to use Loctite, only use "Removable Loctite 242" for very obvious reasons. You can buy Loctite at McMaster Carr. By the way, the threaded rods are 8-32 thread size. I like to use stainless steel wave washers at each connection to the square tube, but that is because I don't use Loctite on it and the elements do loosen up. Everything is available at McMaster Carr. The threaded rod is available in one foot pieces that have to be cut or as studs.  Brad Smith KC9UQR