Here is a site that you can by premade bodies for lake racers.
I am using the measurements to work on the buck for my velomobile motorcycle project.
P-38 Belly Tanks
I just wanted to stoke some imagination here.
If you are going to build a velomobile or a trike, look the suspension setups on the Peel Trident and the Peel P50 micro cars.
Peel Trident Pictures
Peel P50 Pictures
I hope this opens some design ideas
here is a mid drive that I built 14 years ago for my low racer
To Build my mid drive I took one of the following free hub (the left 2 should work).
1) I removed the internal locking sprags for it.
2) I then took the cassette and file out the small splines on the cassette sprockets...
here is a velomobile called the sun rider, that could be made into wood as the base for the trike.
https://sunrider-cycles.nl/en/ and here is the 3d models of it that you could print.
http://www.alligt.nl/bodies/sunrider.html
here is a bike, the designer called the mistress, it is laminated wood and foam and may give you some ideas on how to make a light weight chassis.
https://web.archive.org/web/20110708091857/http://carbonbent.bravehost.com/woodwork.html
I am looking into making a velomobile out of a 1985 kawasaki vulcan motor cycle. the motor will be up front and your legs will wrap around the motor to the foot controls, andthe front tires will be back where your knees are lik a tadpole trike.