When using OBA in SASL, you roll on the Chapter H OBA table to determine the size you get. There is however, no Chapter H OBA table for Allied Minors.
Huh. Well, like I said, it's been a while. My first thought would be "Axis Minors, because they're more similar than different, really," but it looks like they don't have a chart either. I'd suspect that was because it varied too much by nationality, but...
Looking again at the H1.8 chart, it directs you to the Vichy French chart, so I'd use that (Axis Minors directs to the Italian chart, so maybe more different than I suspected).