Sigh... but alright then...
Take a look in one of these re. chronometer:
http://www.subsim.com/radioroom/showthread.php?t=108917
http://www.subsim.com/radioroom/showthread.php?t=167137
http://www.subsim.com/radioroom/showthread.php?t=132339
And if you have plenty of time and want to dig deeper:
http://www.subsim.com/radioroom/showthread.php?t=111832
The "Game Paused" is a tga/dds file, which you just need to replace with an invisible one.
Remember it was done in SHIII, but I'll be darned if I can find the file - at least right now.
But it is there... somewhere...
Re. the Crash Dive to Periscope depth...

don't think it's doable with multiple commands attach to one key.
Think there were some tests going on with open all tubes at once, but without succes.
I love RAF/USAF

but the Zeros otoh...
Quickest way to get her down is to press 'C', then wait untill she's at some 10 to 12 meters depth before ordering periscope depth.
If you press 'p' before, you'll get slower dives... it's like the boats halts and the crew instead goes into a "normal" dive.
But I haven't timed it.
Of course we in TMO crashdive all the way to just above crushdepth