Well.... in clear :
We have :
Hull hitpoints, into sub .zon file
We have Bulkhead hitpoints, into equipment .upc files.
We have compartements hitpoints, into .cfg (seems not works) and sub .upc files
We have items hitpoints, into .cfg (seems not works) and into .upc files.
Sadly into .cfg items have separated hit points, in example, left diesel engines, and right disesel engines, there we can adjust diferent hitpoints to not loss both at same time, but .cfg file doesnt works nay more fot them, into the .upc files, there are no posibility to adjust separated or asimetric hiptpints... sad.
Hull hitpoints seems to accumulate the compartemente hitpoints. Not sure if bulhead are added or not to the total accumulated value.
It means 6 compartement with 400 HP each one, you take damage on all 6, 100 HP on each one, no compartement is destroyed, but if you total sub hitpoints (hull HP) are 500, you are done.
Bulkhead, compartements, hull can be made more strong.
It retard the damage, but when you take it... domino effect is still present disregardoing how stron you made tyour sub.
The crush depth is strongly reduced after take damage.
The domino effect happens with or without Bulkhead damage, so it mus be related to hull instead bulkhead.
Domino effect happens with bulkhead reapired at all, damages reapired at all, and with message "Hull repaired sir ! "
If you takes damage at determined depth, and solve it, this seems to be the limit for next dive, in example, if you take damage at 40 meters, near 50 or 60 you will be destroyed, but surface and 40 meters you can dive normally.
So we need to remember ingame damage depth.... to not pass it never more in the remaining time for the mission.
It is dangewrous, because if you take damage at 20m, and later you watch a plane and perform a crash dive to 40m, you are done...
We can reduce this effect with the crash speed, decreasing the value to minimun to have the chance to recover the sub in case of an above error.
That is i can remember now...