Well I have found them (Thanks for the hint) and yes they seem scripted in amanner that *could* possibly spawn U-Boots with some changes. I muts however do first the hard work of deleting my current, high modified install of SH3 and make a clean one, then create a BLANK campaign file to avoid interferences of other units, and then script a mission with a german airbase set to spawn U-Boots....
If I can have time for all this (Smething difficult these days for me), I'll report
