Normally this cargo rack mounts behind a standard bike to extent the back wheel 1.5 feet back and makes room for its own large panniers, it has a a wood deck on top and plenty of tie down points for heavy duty hauling.
This project is about minimizing the bike and having a compact "sport hauler" where the rider and passengers all sit on the rack. The rack is the only seat, but(t) it's big enough for a couple of people.
The other two bikes can be seen on my hobby website woodenbikes.com
Step 1: Start by looking at what you've got
I wanted to make a compact sport hauler where I could sit on the rack and pedal semi-recumbent.
Step 2: General layout and cogitating stage
I used the cargo rack from the big blue bike and the black rear suspension triangle from the Mongoose bike and the front triangle from a different 16" girls bike.