Not that I would Dare to argue with the all mighty Dick L, who has helped me before and has all those great links (hahaha). BUT, I read in a book that there was a single wheel version of the G offered. I don't know what years or for how long, heck I can't even remember which book it was. But I am positive that it was an option.
I think it was a book I got my father for Christmas this year. I will ask him to have a look.