Hi Dean,
Some serious points to think about,
1. NEVER EVER admit or suggest that you want to, or have gone to 12v, positive, negative or whatever, NEVER EVER. You will never hear the end of it. I own a 12 volt negative Model A pickup as well as a 29 Chevy and I get it from both forums
2. Seriously now, I believe you are correct, it would be the same as turning off the disconnect which. However, fuses don’t normally blow and I believe, if they do, most probably on start up and only once in a blue moon. Get yourself a little mental checklist, ie, Fuel off, ign off, master off, etc
3. Alternator?(tongue in cheek again) GOTO point nr 1 and never mention it again. In fact, I am seriously considering changing my 250SL Pagoda and my E Type to 6v and generator. Maybe even the 911
