I take no credit for creating this method. It has existed on GN2 for over a decade. (Although Gibson and SD still don't have a clue.) A problem exists when a DPDT switch is used to put two pickups in series using the method employed Jimmy Page wiring. There will necessarily be a 'dead spot' in one position of the selector switch. Either the Neck and Both positions of the 3-way will work properly but the Bridge position will be open-circuit OR the Bridge and Both positions of the 3-way will work properly but the Neck position will be open circuit.
There are enough poles available but some folks don't recognize how to make the best use of those two poles.
Here's the strategy, plain and simple. It makes the position of the pickup selector irrelevant.
For any 3-way pickup selector used in a parallel configuration LP, Telecaster, whatever.
(Although Gibson and SD still don't have a clue.) A problem exists when a DPDT switch is used to put two pickups in series using the method employed Jimmy Page wiring.
I don't want to clutter up this thread too much, but I think there is an important thing to point out with Gibson's Jimmy Page wiring vis-à-vis this improved version.
The thing which is commonly overlooked or forgotten is, in Gibson's 'official' Jimmy Page wiring schemes, the "parallel/series" switch isn't: it does switch from parallel to series, however it also simultaneously reverses the phasing, thus swapping from parallel-in-phase to series-out-of-phase.
(At least as far as I'm aware Gibson have only included any type of global series/parallel switching on their Jimmy Page inspired models: first the model from '95-'99 which although definitely takes inspiration from Page's #2 isn't a direct clone; and secondly their much more faithful recreations from 2010.)
It's actually a pretty clever arrangement as with full, unsplit, humbuckers parallel-in-phase and series-out-of-phase are arguably the two more usable tones and the Gibson wiring aims to have those options only a single switching operation away from each other. We also must remember who we're dealing with here, Mr. Page, a big fan of sudden and dramatic volume/tonal shifts, "light and shade", which is what such a switch offers if the phase switch has already been activated -- then the options become parallel-out-of-phase and series-in-phase -- two polar opposites.
So now the "probably at least what Page's actual #2 would fetch at auction" dollar question: how do you create this switching, without the dead spots, with only a DPDT? Well unfortunately the answer is you can't. (In the Gibson scheme's series-modes the 3-way selector must be in the centre position to complete the series-link and thus give any output.)
There is however just a further little twist to this tail, remember we're dealing with the restriction to DPDTs, well that's because Gibson's '90s models used the typical Alpha-style push-pulls and the #2 models have the two pickguard mounted DPDT push switches to handle the PiP/SOoP and phase reversal functions. However the #2 has push-pulls too: on the reproductions HB splitting is achieved with the tone controls, the somewhat familiar SPST equipped CTS 450 series pots; whereas the local series-parallel switching is performed by the volume controls, but this was back before the days when DPDT CTS pots were available and instead they are a part from Honeywell/Clarostat (via State Electronics) -- why is that interesting? Well, these aren't a standard DPDT, disregarding the potentiometers' regular 3 terminals, the push/pull switch has 8 terminals.
This is the point where we depart from certainty and enter the land of assumption, but I feel confident that these are pretty safe.
With eight terminals I believe the switches would connect two pairs of two terminals in each position, i.e. 1 & 2 connected and 3 & 4 connected when in one position -- 5 & 6 connected and 7 & 8 connected in the other. (Think the outer positions of a Mustang slide switch.) This corresponds to the switching specified on page 7 of this datasheet
Where this gets really interesting is that this 8 terminal switching configuration is enough to achieve the parallel-in-phase / series-out-of-phase switching:
In the parallel setting:
the output from the toggle switch is connected to the hot output at the jack socket,
and the ground side of the bridge pickup (and its associated controls) are connected to ground.
In the series setting the above connections are broken and instead:
the 'outputs' from the volume controls are connected together (B+ to N+, forming a reverse-phase series-link),
and the ground side of the bridge pickup (and associated controls) are connected to the hot of the output jack socket.
So, why didn't Gibson swap around the switching? Simple, they were concerned with copying the #2 as closely as possible and already had to make a concession on the bridge pickup bobbins' colour (due to DiMarzio's trademarked double cream). If it was even considered at all, optimising the complex wiring scheme was likely a low priority compared to ensuring they had it correct, which was debatable with their reproductions of Jimmy's #1. Okay so onto the next question and another assumption.
Why doesn't the actual #2 have the switching swapped round? Well that makes the assumption that is even possible, i.e. that it has the eight terminal switched potentiometers, that's unknown to all but a handful. What can be said though is that in the early '80s Schecter were using that style of pot in their "Superock" wiring harness, though the examples I've seen were Allen Bradley branded pots, but it's certainly true they were available and being put into guitars.
There is also the fact that the setup devised by Steve Hoyland makes the most intuitive sense: the splitting and local series/parallel of each pickup is performed by the associated volume and tone controls of the relevant pickup, whereas the global series/parallel and phase functions which control how the pickups combine together are situated closer to a spot between both pickups.
It may also be worth mentioning that rather than completely bypassing the 3-way switch, an alternative wiring could be to use the switch to shunt one of the pickups in the centre position making it possible to have one of either Both/Neck/Both or Both/Bridge/Both in series mode, but for now I'll leave that as an exercise for the reader.