Thanks Steve; that's the best method that I've heard of to-date.
The problem is a "game" problem and you've got a great "game" solution there. I say that because in real life the solution during the earliest months of the war was to stop (or at least attempt to stop) any neutral vessels and carry out inspection as required by the Prize Regulations. A quick review of sinkings on "uboat.net" reveals many instances of "neutral" shipping being sunk after U-Boats followed the procedures required by Prize Regulations.
When the niceties of Victorian behavior were dispensed with later on, any vessel sailing in convoy or otherwise escorted, or failing to show running lights at night and/or steering an evasive ("zig-zag") course, even if flying neutral flag or displaying neutral ID, was a valid target that could be attacked without warning.
As you noted, all that is, or at least was, apparently too much to be coded into SHIII (or even GWX) and the original solution to ID vessels was simply to strictly follow the status of each nation regarding its involvement in the conflict, by "official" date of engagement (and which side it was on, of course). It's not just an annoyance regarding Norwegian ships either, I've been equally challenged to decide what to do about Greek shipping encountered in the first year of the war and Dutch ships seen in the first few months as well.
I think I'll give your "fix" a try. I wonder if it would be a good method for SHIV ATO/OM also; I get tired of letting all those "neutral" ships go by, knowing that the game doesn't care if they're "neutral" or not and will give me full credit for sinking them if I decide to "cheat" a litlle...
