[XenonSurf]

An armed trawler can be sunken with a single torpedo, but depending on the mod you play ships may take much longer to sink compared to the stock game. TMO says expressly that the sink rate has been changed to be more realistic, whatever that means.
I don't thnk the ship renown points have anything to do with ship resistance, but rather with ship importance. A trawler or destroyer is less important than the smallest freighter, a tanker or troop ship should be very valuable unaware of its tonnage, and only big warships are targets which you should go after and therefore should give you many renown points. I think it's related to the ship type and its size which makes sense - but fact is: I don't know exactly, these are suppositions.

FOTRSU has introduced so many new units, so the modders must have a system in mind to set renown points, because the added setting files are new ones, so they can tell for sure what they did, and if yes or no they did change the stock units. For other mods like TMO you would have to compare the files with the stock game files (e.g. with the free tool WinMerge).

The bottom line for me: When I play a serious patrol I avoid sinking escorts or little warships because they have no value for the war ongoing compared to merchands, tankers or troop ships which will for sure resupply the enemy. Destroyers are also difficult targets, I'm not hot to waste torpedos for them, also because I could use that torpedo later for a much more important target. If I have 2 torpedos left and returning to port, this is a situation where I would try to sink a small warship.





XS