Alas, not mathy at all.

The big question right now is that a trailer parts supplier tells me that a drop axle significantly increases the effective axle overhang past the spring perch. Unfortunately, he doesn't know enough to be able to explain it. As I plan to use a drop, I figure that the actual math would be a good thing to know.

HUMMER .25: No need to compensate.

1989 Dodge Raider: 3.0/5
1992 Chrysler LeBaron Convertible: 3.0/A
1994 GMC Safari: 4.3/A