khillr48, fast isn't an issue for me. A tadpole trike at 25 mph is more than fast enough, a delta at 15. I'm a fairly big guy (5' 11", 240), but I have serious physical limitations that are taxing my imagination to solve. Along with only one hand, I have severe diabetes, which has resulted in neuropathy in my extremities - I can't feel anything below my knees, and I only have full use of one finger and my thumb. The second finger works well enough for typing and lite tasks as long as I can see where it is being put, but I have to be pretty careful where it is going when working on things. Because of the neuropathy and other metabolic issues accompanying diabetes, I can't pedal hard or very long. So, power assist is a practical necessity.
Not an attempt to elicit pity; I say the above because as part of my physical reality I have to make allowance for the limitations in accomplishing things.
I design things - always have, since I was a kid. I've designed and built a lot of things, from toys to sculptures to houses and their furnishings. Now, my income and living circumstances leave me with no working space save my living room floor in a second floor apartment, with minimal hand tools. So, projects take a frustratingly long time to reach fruition. Oh well, c'est la vie, eh?
That said, my greatest assett in life is a truly monumental pigheaded persistence. I just keep plodding along, doing what needs to be done to accomplish my goals.. Right now, one of my high priority goals is getting out of that econobox I use for transport, and getting my face back into the wind. What I really, really want is a leaning tadpole trike, with full suspension and optimized steering engineering. Since I'm utterly uneducated as an engineer, I've been doing what I have always done - design my dream after learning all I can find about the project and materials, tweak the design, set it aside while things percolate in my head, and tweaking the design some more.
The rear steering idea has raised the heat in that percolator till it is popping like the old Maxwell house coffee commercial. In my minds eye I can see a tadpole trike with power to the front wheels through both pedals and engine assist, feeding a "differential" and each wheel seperately, with a limited caster range central rear wheel doing the steering. Thank you for getting me thinking in a different direction than I have in the past - for myself, finding and implementing workable solutions has always been "Job One". The world is designed and built for two-handed people with well working legs, so I have had to evolve my own approaches to problems.
You rear steering system intrigues me, and seems it may be a near ideal solution to one of the biggest issues I've encountered.