So, we've discussed doing this before, and I can see people not understanding what I'm talking about without visuals, so I took pics of my A8 Invader mag swap.
Invaders, Dirty Fingers', and 500T's have 3 oversized magnets in them. Duncan Distortions and a whole bunch of different Dimarzios have 1 oversized ceramic. You can replace the 3 with one (or vice-versa if you have a triple mag set). I'm replacing the 3 mags with a normal sized A8.
Here's the material I used for a spacer to place under the magnet. It's just fiberboard (like MDF) in the same thickness as a normal magnet. I just used the magnet as a template and cut it out with an exacto.
Here's the 3 magnets, the two smaller ones go outside of the pole screws, N-S orientation is the same for all 3 (same for 500T). In a newer DD the spacers are plastic, same size as these magnets.
Pickup put back together, I just used some wooden spacers from a dismantled pickup. You can see the vertical orientation, as opposed to flat, as they'd be in a pickup with a normal sized magnet or normal pole screws (in the Invader I have to use a spacer because the pole screws do not penetrate the baseplate).
In a DD you can just put the pickup back together like any other pickup and it will be fine... if you have the shorter spacers. If you've got the big plastic spacers you'll have to make some short ones or pirate them from another pickup.
The fiberboard spacer underneath the magnet looks darker in color because I have used it for this purpose before and it's been in the wax pot before, so it has soaked up some wax.
Notice my plastic tape reel for storing the original fiber tape for reuse. If you're careful taking it off you can reuse it 90% of the time, and it doesn't look like a hacked pickup.
Here it is all taped back up and ready to install, looks as good as when I pulled it out of the box yesterday.