I dunno why none of us old fahrtz didn't think of this earlier, but from the
RFB 2.0 ReadMe:
Adjusted default surface speeds for all boats (credit to virtualpender for finding the info) as follows:
-Fleet subs: 6, 12, 15, 18, max speed for each respective class
-S boats: 3, 6, 9, 11, max speed for each respective class
I "assume" (such a naughty word) that they mean for Ahead 1/3, Ahead 2/3, Ahead Standard & Ahead Full, but no mention of that. Still, it might help a bit...