To follow ground terain.. you really wouldn't want a fixed, non pivoting front axle would you?
I'm kinda surprised that the extra considerable weight of a front axle and associated linkages and kingpin setup wouldn't offer any advantages over a narrow front end. Seems like the weigh difference alone would change the tip point on a hill.
Stability still seems like it would be an issue.
perhaps in a static tip test.. not a smuch.. but if driving, on a hill, and the narrow front falls in a hole, seems like the tractor would lurch mor ethan if a 4 wheel vehicle had a single wheel fall in the whole, as with the wide front, the tractor actually doesn't dip as low to the ground, due to the fact that the one high wheel and the low wheel are going to average the height of the tractor. In other words.. set a varrow front end in a hole.. then measure ground clearance from bottom of front of tractor to ground.. then take a wide front.. se one wheel in a hole.. measure ground clearance. Seems like the wide front will retain more clearance, as the pivoting axle is averaging the 'drop'... axles becomes the hypotenuse, ground is the long flat of the triangle, and the distance from ground to the 'high' axle is the short upright flat at 90' to the ground.. etc. More or lessa right triangle..
Soundguy