Beautiful, anzacmick, absolutely beautiful!
You, sir, are not only a genius but an extraordinarily gifted artist! I love how you've made the holes and torn metal vary according to the ordnance that hits a vessel, far better than the merely blackened scorches seen until now.
It's also good visual indicator for judging how much damage you're dealing as well as how much has been dealt to yourself in turn (the latter being a more realistic way of gauging the health of your u-boat, rather than the Hull Integrity % or those rather vague blackened spots).
The brightness around the edges of the holes seems a bit out of place, though. Maybe darken that just a shade or two, except for right at the very edges where you might expect to see shiny metal from being sheared apart by the blast.
Will any of the three u-boat damage decals reflect crumpling of the hull from indirect hits by depth charges detonating outside the lethal range?
Seeing my u-boat blackened from damage was already distressing but your mod will make it absolutely disturbing to view the damage and knowing I'll have to dive with those weakened spots in my boat's structure.
I can hardly wait to see the end results!