Thanks @
brianinc-ville you are right. I should have done more research before posting.
I am thinking that if I can get a tandem for around $100 that is solid and worthy, then building it up to a long tail cargo bike might be within financial reach. I would like to fabricate a XtraCycle style rack system. I would like to do it in a way that I can always return it to a Schwinn Twinn. I don't know why. There is no logical reason for this. I would prefer everything be bolt on. I have five attachment points in mind. They are as follows:1. Rear dropout eyelets left side, 2. Rear dropout right side, 3. Seat post, 4. Stroker's stem with a cut bar mounted attached on the left end and, 5 Stroker's bar mount right side. I figure this should be pretty sturdy depending, of course, on how well the rack is made and the materials used.
I thought someone would tell me not to start with a Schwinn Twinn because they are too heavy to start with. The problem, so far, is that other tandems are far more money. Even Schwinn Twinns go for what I think are crazy money. $400!?? One factor in my favor is that I live on the south shore of Long Island so any cargo runs will be relatively flat. I might even get by with a three speed.
On the other hand, my preference would be for something like Bilenky's Chuckwagon cargo bike, if I could swing copying that in some way. Start with a rear triangle and build forward. We will see how things go.