I found some trailer springs that were 1-3/4 inches across. I can work with this.
I'm thinking of
I'm thinking of using one of these for the rear transverse springs, and removing most of the leaves to make it softer and lighter.. I looked up how to soften leaf springs, and apparently removing the shortest leaves will do the trick.
Someone suggested a swing axle setup for the front, and I think I'll go with that. I know these are just asking for trouble at high speed--but I'm not going to be going THAT fast.
There is one other reason I want suspension: Some of the businesses in my town have driveways that meet the road at quite the slope, so either I'd have to make sure I was completely out of the driveway before turning (leaving me way out in traffic) or end up on 2 or 3 wheels momentarily (with major torsion stress to the frame) as I turn out of the parking lot.
UPDATE: The gentleman who built the Nephew of Fantom told me that his ride weights about 83 kilograms, or 182 lbs. That does, however, include an electric assist system, which mine won't have.
UPDATE 2: I'm lengthening the nose and rear by 6 inches each for better aerodynamics. I'll still look at that kayak skin you suggested, squirtdad. I found a video on it, and see how it hardens, and how sturdy it is. Maybe I could even use it for the floor.
Can you use Tremclad paint on it? I want to paint this medium blue (I have reasons.)