While it's hard to beat aluminum for its strength to weight ratio, the ladders were really overkill in the strength department. They are capable of holding several hundred pounds of load, while we only really needed to use about fifty pounds of cords and lights. I looked at several (many, many) material and design options to replace the ladders. I needed something lightweight, easily portable (probably modular with sections no longer than 8-10ft), durable, cheap to build- requiring no equipment or skills to which I did not have access, and able to span 20+ feet with no center support. That last one was the killer. Lots of things can span 10ft. with no problem, even 15ft. if pressed, but 20 or more feet with no center support and you start to have troubles. In order to have the strength to span that distance and hold any kind of load safely, your truss starts to become huge and heavy, and its own weight becomes an issue. Although I had trouble with using wood as a material for the upright posts (warping, splintering, etc.), it gave me the best strength to weight ratio that I could afford. After looking into several truss designs, I decided to make telescoping sections of square tubing out of 3/8in. plywood.
I wouldn't have been able to do this last part a few years ago. I just learned how to use a MIG welder at my current day job. I'm no professional welder, but I get by.