Re: What do you guys think of this combination?
Yes, Custom/'59 are a great, versatile pairing. It's hard to recommend alternate options without a bit better idea of style/tonal tastes. What amp or pedals you use can't hurt, either.
The Custom is a solid pickup, in the right guitar it's one of the few ceramic humbuckers I like. It's a bit like a bigger PAF with more punch & bite. Strong for a lot of styles, but it's got a bit more of a snarl than scream on leads. If you want a punchy, slightly brash but not quite harsh pickup, it's a great choice. I particularly like it in all-mahogany Les Pauls for a heavier rock sound.
Custom 5 is a great option for some guitars, but in others it just has too little in the way of mids. I see it as more of a fix for a problem guitar, than a general pickup, but I don't have a lot of personal experience with it.
Screamin' Demon is an interesting pickup, it's a bit like a growlier '59, less treble overall but a bit more bite. Despite extended bass response, it's less prone to congestion because of the all-screw design. Very flexible due to mix of screws, can do things like shuffle the screws so all the hex heads are under the bass strings, to give smoother high strings and more bite on low strings. Or swap them all out for all 0.75" fillister or all 0.5" allen head. But it's not a high output pickup, output is similar to a '59. May not be what you want out of a bridge pickup.
I switched from a JB to a PATB-1b in my Ibanez RG570 (basswood, was just too thin and inflexible with the JB), and it was just perfect for my needs with that guitar. Can pull almost any tone I want out of it. Ridiculously more responsive to volume/tone control adjustments.
I love the way the PATB-1b crunches for low gain rhythm more like a lower output pickup, but grinds in high gain, and sweetens up for leads. Sings and has great harmonics, but not in the exact same way as the JB. It's sort of like a Custom 5 for rhythm with a bit more Custom Custom flavor on leads (with more treble yet still smooth), but higher output than either. Has a mild mid scoop, I found backing it away slightly from the strings gave a very even tonal balance.
PATB-1b's caveat is that up close it doesn't look at all like a conventional pickup, and covers wont fit it (and it won't fit in the pickup cavity of most guitars if you did get one that fit).
The problem with the STK-4 (or even worse with duckbucker) is that if you combine it with split humbuckers, you want to split it as well, so that it cancels the split humbucker's hum. Humbuckers only cancel their hum in series or parallel modes.
If you don't use the single by itself much, easiest solution is an SSL-2, that gives you hum-cancelling in everything but the middle position. Where the STK-S4 wouldn't hum by itself, but wouldn't cancel the humbuckers hum in the 2+4 positions.
That's why I mention the megaswitch, which lets you wire each position independently however you want, but is a bit more work to wire.
