He's talking about 2-3 minutes to get under, something uncorrected it, so I would advise checking. You never can tell which mods overwrite other mods modifications or who has mod soup. TMO version I have sets the Gato main ballast at 48000 and leaves the dive ballast at the default 9000, what I did was set main at 38000 (little less than double) and the dive at 18000 after a bit of trial and error. Oddly that gets the whole sub under in less time with P rather than C, since crash dive takes a steeper angle so the stern sticks up longer. Either way it's about 35-40 seconds from the klaxon to the periscope shears going under, faster than that would be too much like supersub.
Running decks awash (25 to 27 feet) it's about 15 seconds to periscope depth.