[Christ]

cornering stability and tire loading. A reverse trike has the ability to swing-ass, rather than tip on it's face, like delta trikes.

Both right side pics were tadpole trikes.

I can't think of an instance where you'd want the front track width thinner than the rear, because under heavy loading, the vehicle wants to move fore and in the opposite direction of the curve which you're following. There is a fine line between stability and rolling over.

Imagine that there is a straight line between the center lines of the rear and front hubs on the side opposing a curve. The closer to perpendicular the moment angle is to that line, the less stable you're going to be as far as rollover performance. Traction performance is exactly the opposite. The best available compromise is a 45* angle to that line at maximum angle, which is with the two available lines parallel to each other. (each line between left and right sides), which means that the track widths should be equal, or very close to it.

The reverse (tadpole) trike design is inherently stable when the weight is about 70/30 with the front tires bearing the most load, approx 35% per tire, and 30% on the back tire. If the layout of the reverse trike is a right triangle, with each tire 90* from the next, this places the moment angle on the hardest cornering exactly parallel to the front tire opposite the curve, which lifts the back tire. In this case only, you'd want more than 30% of the weight on the back tire, maybe 40-45%. Most of these designs are not right triangles, though, rather closer to Isosceles, meaning that only two sides are equal.

This would place the track width more narrow, closer to the lower right image, which gives greater chance for rear end swing if the weight isn't properly balanced. Of course, proper balance means a trade-off for traction on the drive tire. The fix for this would be to place ballast weight on the rear tire, and maintain a FWD drivetrain, with two driving wheels, which completely changes the handling characteristics.

Keep in mind, that everything in this post assumes that you're coasting through a curve, with only angular load on the rear tire, not accelerating or braking.