James, you are technically correct in what you are saying and it is obvious you are very educated on port, but for the average wine maker (most people here) that is not practical. I think we all realize that what we are making is "port style" wine, not a true port. Trying to halt the fermentation by adding brandy may work but it is going to be guessing game as to when to add it. There is nothing wrong with making a "port style" wine by adding brandy at the end. Even RJ Spagnols call theirs a port style wine, not a port. It is my understanding even if you did it the technically correct way then you could not call it a port unless you made it in Portugal.
I have several different true ports myself, 11 different vintage ports, 3 unfiltered lbv, 1 filtered lbv, 1 tawny, 1 20 year tawny, 1 white and 3 reserves all totaling 104 bottles.
I think we need to lighten up a little on port vs port style debate, after all most of us are just here to have some fun with it. Sort of like me calling my Apple Pie Moonshine, I was called out for calling it moonshine but I think everyone knew it was not real illegal moonshine.