Well some people place the 688i at 31kts!
I seem to remember that the speeds in SC were a bit lower for American platforms and a bit more for Russian platforms.
Honestly, the platforms speeds are mostly relative and no one knows. In the same board I read 31kts was max speed for 688i, I read that the SW made 45kts. I have no idea.
If I were going to make changes, I'd do it with more relative concern, and it seems they all fit together pretty well, although I'd like to see the Akula I Imp move faster than a 688i.
But messing with stuff like that without real data is messing with a core aspect of gameplay, so I have to be really convinced about it, and nothing I've read about submarine speeds has been convincing to me. :hmm: