I may not understand exactly what you are trying to do, so forgive me if this is off base. There may be a reason the project you saw os difficult to find. Your description reminds me of the Trek/Fisher which got some mixed reviews due to the amount of rack extending past the rear wheel. Once loaded it makes the front end very light and the whole bike becomes skittish. Add to that the whippy frame flex and it doesn't sound so good. I haven't ridden one, but I have looked at them. I could see what people were talking about.
The boda has a high rack (allows for an under deck battery+fender clearance); however, the frame is remarkably stiff. The deck is also quite a bit shorter than the one on my Dummy. My wife regularly carries our two kids with panniers full and it's not squirly.
If I was going to build up a standard frame to carry big loads I would start with an old school MTB that has really long stays(by current standards), and keep the cargo over or ahead of the rear axle if possible.
--- In email@example.com, "diy141" wrote:
> Anybody have links or references to building your own Half Xtracycle.
> An xtracycle on a regular bike, with no wheel extension? Still strong enough to support a person sitting in the back, but less of a footprint.
> Saw some pictures somewhere of one... Thanks!