The 2 wheeled flevo is useless when roads get slippery. The front wheel drive, the heavy front piece, gets you down with the first sign of ice or snow. The solution here has a stearing tube in between the rear wheels and the bike. This allows for leaning in the curv.
I couldn't make the rear part fixed, because the rear fork isn't really strong enough. And it work good enough on ice. I still could fall over, but it didn't happen often anymore. And when it happened, the bike sort of layed me gently on the ground.
We tried to make a back to back tandem.
It didn't work out, we felt the steering angle was to flat to control the bike. We had to steer with all our might to keep the front piece from flopping over.