No mods have crush depth markers. Some have design depth markers in red, but those can be safely disregarded. We didn't change anything about sub durability from what we inherited from FOTRS. I took a Porpoise down to about 650 and came back up when I heard the glass breaking sounds. At about 375 the sub died, so crush depth isn't treated like some mods. You take accumulated damage until you die. I like it a lot. Nobody knew what crush depth was for their sub in the war. We shouldn't know either.
Now I'm going to channel Ducimus. This is a supermod. It specifically is not compatible with other mods, especially environmental mods. The environment in SH4 isn't just eyecandy, but invades all aspects of your and the enemy's detection, the ability to lock the periscope, yada, yada and so on. Also, FOTRS Ultimate pushes the limit of the game's tolerance for monkey business to the uttermost. The mod you add might be your last!
That being said, we stuck to the JSGME installation because we don't want to be in a position of telling you how to play your game. Some great things happen when players try something stupid and something really great happens.