My wife is the handcyclist, not me. She would never be able to use a two wheeler because of her lack of trunk stability, but has been able to play with several 3 wheeled designs. My first thought is will that design turn ok at low speeds? I have seen one in person with a steering lock with the hands used as stabilizer and initial push off like a luger until fast enough to be stabilized. Interesting project none the less and good luck.