That might be fun to try, but you might need a wider track than the standard width of a H14. It would be easy to extend an axle out on each side. It would have to be removable so you could transport the craft. The rear axle might have to be located behind the tramp a little also. You really don't want to capsize at 60 kph if you are on hard ground. Keep in mind that you will elimate almost all the friction that a boat on water has. This means that you could easily reach speeds that could be very dangerous. If it would be possible to make a single front wheel, it sure would simplify and lighten up the steering. The trouble with that would be the front corner clearance if you were to fly a wheel. I'm sure this has been done before, so maybe you'll get some other responses.
Good luck,
Jack
P.S. How big of area do you have to operate on? (flat, tree less, etc)