Heck, if you want to add realism, I suggest you get a basketball or soccer ball and stand on it while using the periscope to set up your attacks and firing solutions. That at least might come closer to how a small vessel heaving in heavy seas might feel like.
Better yet, put on a diving mask, and every 20-30 seconds have someone heave a bucket of water at your face. And no, you may not wipe the face plate clear with anything afterwards.
Time compression is just a means of making the experience available to people with real lives and jobs. Who can actually take the next several years off to do nothing for 24hrs a day but play a campaign of Silent Hunter?
P.S. I normally criuse at about 8 knots (1/3rd telegraph) - seems to give me about the maximum range possible with the minimum fussing (I suppose extreme fixation on speed settings and sea state & weather might squeeze a few more kmiles but I'm just not prepared to be that anal about my telegraph settings
)