Looking to put together a couple of Trek 950s as a tandem. Looking for a local source of suitable tube to accomplish this.

I can't afford a high dollar tandem, but want something better than a Walmart bike. Even though we won't likely be doing much more than flat area rides at relatively slow speeds. I'm a bit under 300#, and trying to get back to my former glory weight of 220 (but would be happy to just get to 250 for now!!!). But more seriously, my wife has medical issues that preclude her from riding a bike on her own. Not stroke related or such, but balance and strength issues.

I decent at fabrication of heavier metal items like Jeep and truck brackets and such. But haven't brazed in a very long time. I've read probably everything out on the web concerning do it yourself tandems. I've been away form the cycling scene for over 10 years and regret it deeply. But I've pulled my MTB out of the shed and rehabbed it and after clearing with my doc about my knee (and a cortisone shot), am putting some distance under it again. My wife looks forward to riding, but is incapable of managing the balance on her own anymore. We ARE considering a trike... Anyone know how to make one?