I'm sure you could hook the SHR up but there would be a significant gap. The pickup cavity underneath the SH-1 is just a square(ish) hole routed into the wood. The wiring should be similar since the SHR1 is just a humbucker in a smaller casing.
That begs the question - what are you after, actually? For those bright and clean single coil tones a Duncan P-Rails should cover the ground nicely without having to look at a gaping hole in the guitar :) It is also possible to wire the neck humbucker (SH-1) in 'split-mode', where only one of the two coils is in use. The tone would be somewhere between a true single coil (think of Stratocasters) and a humbucker.
That's true. Hadn't thought of that option.
I'm trying to put-together Teru's Forest GT Custom from the band Versailles. I've got it almost identical except for that stupid clunky sh-1 up front. Hmm... would it be possible to use the sh-1 mounting, take or cut-off the sh-1 pickup, and screw-on the shr ?