Yeap, you can only fit a pushpull pot in the vol pot.
But.
Heh. I am embarking on a mini mod that requires no drilling to my Saber but can provide up to 3 additional
mini switches. In lieu of the main pup selector.
Or 1 3-way pup selector (gibson style) and 1 (maybe 2!)mini toggles.
In a nutshell, take a look at your pup selector. Its sitting on a piece of plastic. Open up the cavity. You will see, beside your pup selector, 2 nuts, unscrew them, you can take out that piece of plastic. You will see you have a rectanglar hole and 2 holes (for the screws of that piece of plastic). Now, you can DIY a piece of arylic, or wood, or metal, into your desired shape, poke 2 holes, get 2 screws to hold it onto the body, and there you go. Space for more mods.
It ain't uber fantasic, but if you got limited space, you could might as well do it.
In my case, I can think of, a H-H saber. Do the mod. Have a 3-way toggle, 1 on/on
mini toggle to handle coil split for both pups. OR. Have a 3-way toggle, grab a 4PDT 3-way switch, to handle series/parallel/split for BOTH humbuckers at once.
Oh, yeah, you might, might might... need to sand that rectangular hole on yoru saber a touch wider to accomdate the 3way selector.