I like the digital model you posted. I am eager to see how this works out. I have been considering building a front drive recumbent from some scrap bikes too. I may go with 700c front and rear wheels though.
May I suggest that you try a more conventional steering arrangement at least till you see how it goes? It would be easy to change later if you are set on understeer. If your model is accurate, it looks like you could drag a handlebar in a corner and set yourself up for a really bad crash.
