I too... like the IX, as well. Namely for its longer sea legs & that it holds more torps than the VII's or the II's do.
Just as you do, I too, run decks awash, having set the subs up (been a bit since I looked into that area so can't recall the exact file in the uboats depth setting for what's considered surfaced & at what depth kicks in the e motors
) to do just that... as that was & was used as a viable tactic.
Heck, Fubar... send 'em off to kiddie garden & graduated college... feels more like to me, kiddie garden-graduated & had k schoolers themselves aka gran kids... before ya hit 20 meters, Myself...
to be frank about it...
but, yeah... it does take an exuberant amount of time for it to claw to the depths... compared t it's smaller, more agile kin.
Think I timed it once, just to see if the dive time was... accurate on going from full out surfaced to peri depth... & wasn't shocked to find... it was waaaayyyyy of base. took something like 5-10 seconds longer than they were supposed to, at minimum. If I have it right, the time is only slower than the VII by about 3 to 5 seconds... & most mod sets I have, the VII's like oops... aircraft... pop the cork... bam, submerged lickety split... almost as fast as a II's time... the IX... same scenario... oops aircraft, pop the cork.... & (que cheesy elevator music to hang oneself by....) aircraft attacks, drops bombs, strafes ya... drops some more bombs or DC's if it's so equipped... & strafes ya some more... in all the time, while you're wallowing about like a addled whale... blundering about... lost in a daze.... before ya submerge.
Can't believe that someone, hasn't investigated that... & offered up a fix on getting dive times right... I would, if... IF... I knew just what files it was that controlled that aspect.
If it is a .val/.dat/.zon... or anything related... forget about it... don't have the knowledge, items needed, or the time to attempt to learn them now... old dawgs & new tricks... move along... BUT... if it is like... .cfg or similarly related... then, I am quite capable of tweaking it or making tweaks to it.
I know My limitations... thanks.
M. M.