Now, in Stock and most mods, you should get 300 renown points for a successful insertion, sometimes more. You do not lose points for failing. Sink Hospital Ship though, and you will incur a -2500 hit in FotRSU, just for the ship, and similar in other mods. Sink a "friendly", and it is a minimum of -5000 points penalty, and more for the ship itself (whatever its renown value is). Other than that, it is difficult to get a negative score...
