All good points. The main reason that you most commonly see 2" spacers is so the factory studs don't need to be trimmed.
I can't remember the spacers I bought off hand, but it was either 2" or 2 1/2". At least they were supposed to be, I never actually checked, but whatever they were I still had to take a cut off wheel to all the studs and whack off (giggity) about a 1/4" or so. Didnt learn that till after I scratched up one of me freshly powder coated rims.
Such is life. From a 1992 Wheeled Coach with to the best of my knowledge D70. Just fyi and all.
I did a bunch of measuring and guess-timating on the spacer size, wanting to go as little as possible and still get the axle where I wanted it, and in the end figured I could have used about an inch less and still been happy.