Thanks hugely, Stiebler. You've passed on some very important information there, things I didn't realize or didn't think about, particularly the consequences of alterating original files.
Also didn't know that the schnorkel-mounted rwr displaces the radar...in all the discusssion of this glitch, thats the first time I've been told that!
Anyway, I've got the day off, so I think I might just go for the clean install and then do everything via JSGME.
Thanks once again, you have been very helpful.