Brick, you got caught up in the "dig up an ancient thread" syndrome. Askgary replied to this thread as if it were posted yesterday. Askgary, no matter how hard you try that will not work. You'll never get the two devices close enough to use a two gang plate. Besides, the way you describe is quite non-code-compliant. You'd have to do more to make it complaint, and even then it would still be nearly impossible to get a plate to fit and would still be hackery.

The last guy couldn't figure it out either, that's why there's a subpanel - he left the old service in place because he was confused to heck. Find the smallest-value fuses you can. Replace all of them with that. 12.5A isn't a normal common value anymore, so I'm going to bet that one is the oldest. You should probably try to find more 12.5's and use them in all of the spaces. The problem you're going to find with your incremental replacement is that all of those circuits are going to tie into each other in ways that make no sense to you. A 'hot' wire is going to go up in the wall in one room but the neutral to the same circuit is going to be going the opposite direction in a totally different room. You're going to run a new circuit to one room and when you're pretty sure you're done with all of the k&t wire that goes to the old circuit you're very sure you followed, you're going to unhook that wire and three things you thought were completely unrelated are going to stop working. Been there. Done that. I enjoy the challenge, because this is a bit of a hobby to me - and the history of it is as interesting to me as the work, but if you're a "normal" person with a real life... I feel for you.

Update: I spent a remarkable amount of time up on a ladder yesterday working on the wiring in the bathroom. The situation in the ceiling and space above is interesting. 1 - It appears some of the ceiling is 2 layers of drywall with the original lath underneath it. Other areas seem to be more of a sandwich of drywall, plaster, and lath. 2 - With the help of a prybar, I was able to finally remove the old shallow fixture, which had been buried twice - once in a remodel where they built the wall over half the box, and again when I had drywall put over the ceiling's sagging plaster. 3 - Once I uncovered the box, I was able to see that the wiring coming down from the cavity above is K+T, which was spliced to 14-2 NM. 4 - Mineral wool seems to really irritate my skin. My arms looked like I had mild sunburn all day yesterday! Any tricks for keeping this stuff up where it belongs, rather than falling out all over the place? By the way, the K+T isn't buried in it, but seems to be running above it and coming down. So at this point, I'm running into a couple issues: 1 - A standard remodel ceiling box isn't going to do a great job of fitting over the multiple layers of ceiling that are in place. Since most of them aren't even fixture rated in the first place, my thought was to cut a hole where I want the fixture and use a fan-remodel brace and box. However, the same issue is showing up -- the thickness of the ceiling prevents the brace from attaching to the box. Do they sell extended length boxes? Certainly others have placed drywall over their plaster before, and have had to contend with this. 2 - Because of the location of the old wiring, I'm not sure how exactly I want to deal with splicing the 12-2 to the K+T. Remove and replace isn't a viable option, and the K+T is basically in good shape. See issue 3. 3 - I'm now the proud owner of an approximately 6x6 hole in my shower ceiling where I freed up the old box. This hole runs in the same joist bay as the hole for the new fixture, but I do need to splice 12-2 a few feet over in order to power the new light fixture. I thought I could use a remodel box with a blank cover, but that seems to not be bearing out very well, either in terms of cutting out the hole for the box or getting the fit right. Anyways, those plastic cable clamps and the K+T are a bit unnerving. So I'm back to thinking that maybe an access panel makes the most sense, in terms of keeping the splice accessible, but I still need to put it inside a j-box, yes? Does that j-box need to be fastened to a joist? Thanks all - this project was supposed to be a couple hours, but has bloomed into a couple days.

More wishful nonsense. You need to understand what a "listed" product is, and what that means. The divider is specifically listed to divide the box to a degree short of making them two physically different boxes for the purpose of putting separate voltages in each side. It is NOT listed to make the box into two ENTIRELY separate boxes for the porpose of abandoning half of it behind drywall. PERIOD By your logic, I can put a curtain across the middle of my living room and sell my house as a duplex. The listing on the divider is just as specific as the listings of wire. You can buy a 16 gauge lamp cord and use it in your house, but the minute you try to put it inside a wall, it becomes a code violation. You can use 14 gauge NMB inside the walls, but the minute you try to put a 20 amp breaker on it, it becomes a code violation. You can put a divider inside a box for the purpose of putting two separate voltages in a box, but the minute you try to use that divider as an outside wall of a box for the purpose of covering up half the box, it becomes a code violation. There is no way you can drywall over a box that is supposed to be flush with the finished wall surface without putting the drywall in the box. You would just be violating the codes in different ways no matter what fool reasoning or method you keep coming up with. The only benefit anyone is getting from you bumping this is A GOOD LAUGH. Just because you just discovered dividers, does not make them the cure-all for your laziness of not wanting to do this correctly. I have been using dividers correctly for over 30 years, on a regular basis. Believe me, I have known what they are allowed to do long before you posted a picture of one here. "There are lots and lots of dividers for sale on the Internet that are used for this." --Just because you can substitute the word "this" for "the purpose of putting two different voltages in the same box" does not mean that you can then turn around and add "illegally covering up a box" into your own definition of the word "this".