Wow, that is pretty cool!
I thought the only thing I could do was put them in series, but one on each pickup or in parallel, now that is nice.
So, the original Gibson one on my Blues Hawk affects bot pickups, so I'd have to get it rewired to separate them out and put one varitone on each pickup, right?
My aim is to increase the number of tonal variations I can get out of the guitar though, so one on each pickup wasn't what I had in mind, but more like both on both pickups so I can add both effects on both pickups in any position of the selector.
Now, if I have two varitones in series, I can put one on bypass and just get the effect of the original varitone. I think I need to have a chat with bigDguitars to find out exactly what to do, and also with a luthier to see if I could even pay for the mod...