I DID IT!
Sorry for my excitement, this was quite a leap for me, not tried any pack3d stuff before, combined with 3D coordinates, hex-editing and some other things I'm not very good at.... Been working on this most of the evening, so quite a learning curve... and please I managed it, been meaning to take the plunge with dat files, models and textures but was putting it off..
anyway, the CVE_Akitsu's rudder, now stays attached to the ship all the time and the lightmap, texture, normal map TMAP etc are back to normal!!
While maybe not the most importnat bug, I'd noticed it and that was enough to annoy me..
If anybody wants this tiny bug fix here is a link:
http://mpgtext.net/subshare/690NCVE_Akitsu.dat
The dat file goes in your Ubisoft\Silent Hunter 4 Wolves of the Pacific\Data\Sea\NCVE_Akitsu folder...
What next....
Hmmm.. maybe some nodes for more ASW weapons on Jap DD's, fixing depth charge texture.. dunno yet...