I usually just use the mod installer to install my IX skin's in OM, just put activate them and they show up, I still have a few skin's around also like Carotio's camo for the type IX.

http://i411.photobucket.com/albums/p...120021_090.jpg

http://i411.photobucket.com/albums/p...081359_029.jpg

To clarify, i'ts no problem to copy them in the game and the first skin shows up ok. But there are three different skins included, and I don't know how to switch those in OM (not vanilla).

hmmm, In my files all the skins are seperate, not sure on these working in OM as I was, the above screen shots are from the stock U Boat expansion or SH4 Gold with out any mod's