Thanks Logar
Thats the same thing I have been fooling with except been trying to mod a Porpoise, but still getting the "encountered error report to Microsoft" crash every time I try to load a campaign mission. The Save files are in the SH4 folder in your My Documents folder, I just found a bunch more of the .upc files there as well so going to try some changes to those and see what happens.
Schlag for more speed get the Sub Sim Tweak files from
http://hosted.filefront.com/aragorn155/1928452
And SH3 Mini Tweaker from
http://www.delraydepot.com/tt/sh3sdk.htm
Put the SH4 tweak files in the Mini Tweaker SH3 tweak files folder, when you fire up mini tweaker use the alt game folder button to select the "Silent Hunter Wolves of the Pacific" folder in your program files directory. Then go as fast as you like =)