Though it doesn't relate to Alembic pickups specifically even though he tests a couple, there is a series of threads on Talkbass (titled Dr Dimentos...) where Ron routed out a big bathtub in two of his basses between the neck pocket and bridge and has tried literally dozens of them in all sorts of different positions. Makes interesting reading for those curious about pickup placement.
http://www.talkbass.com/forum/showthread.php?t=111547

Somatic, thanks for your offer on looking into it if I need help.
 
The problem I have sometimes, is to make myself understood, on many occasions, when communicating via emails, it would take so many exchanges and lengthy conversations to get things cleared. Sorry, if this is one of them, this happened before.
 
Regarding the four positions PU selector and its various settings, first, the Luthier is going to have to work it out, as I wasn't able to get any info on the pins layout, but my request is like so:
1) Bridge + mid PUs share a Filter+ Q-switch, neck has its own Filter+ Q-switch.
2) Bridge + neck PUs share a Filter+ Q-switch, mid has its own Filter+ Q-switch.  
3) Mid + neck PUs share the same Filter + Q-switch, bridge has its own Filter+ Q-switch.  
4) Probably Standby
And the PUs that are sharing the same Filter + Q-switch will have a Pan pot as well as a volume
 
That's what I want to do.

Bsee, I am with you on few things. I did not understand at first what you said about the MXY.
 
I understand what you're saying about PU placement and more/less variations, I though about it, but the thing is I do slap as well, and the PU too close to the neck is not great for that (me at least).
 
Further, you answered something that relates EXACTLY to my post, SPOT ON! you say: Looking at your proposed setup, the spacing is going to be awfully close between the pickups such that you won't get as much variation to play with. This is exactly why I wanted the third filter + Q-switch! So, I am aware of this, and for now, the good option is the PU/Filter selector trick that I described above.  
 
Regarding placement, again, I am with you, I would prefer the Filters closer to the PUs, but I am trying to keep things tidy and minimize cable extension, because the Q-switches would be further away from the Filters and would require some extra work. Anyway, you are right, I am going to get this positioned properly, after all, once it is in the cavity, who cares what it looks like!?
So the volumes will becomes the Filters and vice versa.  
 
Thanks for pointing this, this is very important. I did think of it, but now I am going to get it done properly for sure. Luckily, the Luthier hasn't stared the wiring yet. Now, I have to decide where to fit the Filter selector.  
 
Somatic, thanks for the link.

I didn't want to give the impression that I was asking the typical X vs Y questions, such as; brown vs dark brown, which is best?...  
 
Dark Brown - no contest.
 
 
Best way I know to clear a room is for me to pick up my Peavey T60 and start making noise with it
 
Peavey T60 - unheralded good basic instrument.  Haven't run into one of these in years.
 
 
I am going ask the Luthier to use the PU selector (which I wasn't going to use), and turn it into a Filter Combination selector!
 
LG:  This might just be the bee's knees for studio work, but if you play live you might want to think about the ability to switch on the fly.  A former denizen of these parts has a Series I and a Series II - both very beautiful basses.  He prefers the Series I for just this reason - he feels the Q switches are easier to use in a live situation than the CVQ pots.  Some believe there is such a thing as too many controls.  My Alembicized Fernandes has one master filter and 3 position Q only.  It works fine and I don't notice much of a disadvantage versus my Series I which has  a separate filter & Q for each pickup.
 
Hemp - Lifeline to the Future!
 
Bill, tgo

Bill, so you prefer dark brown then? I prefer dark black!
 
Well, I don't do gigs, so the more the control the better for me, the bigger the sonic palette the more flexible and enjoyable it is.  
 
I usually run the software called Live by Ableton, and I jam over drums loops, chords progression/guitars and so on... the drum sound always change, I never stick with the same drum kit/sound and groove, then I also jam over real finished song...    
 
I can happily recommend this software for jamming, its loop orientated and optimized, and it syncs automatically virtually anything, and if you don't have sample loops, you can always chop any parts you want from an existing song, and dump then in Live and it will sync it in real time. Although, depending how you trimmed the loop, if it doesn't lock properly, you can also adjust it in real time.

Ah ah! I can see that Alembic has done this PUs placement before although as a dual PUs... I am happy to see that. I enclose a photo;

Hi Somatic, in case you're around, I posted a question over there:  
http://club.alembicguitars.net/Images/393/32671.html?1161708023
 
Would you be able to advise or help?  
Thanks,  
LG

Then there is Ernie's Custom Orion from a while back.

And there is Barry's Triple Pickup Rogue - if only photoshopped.

OK, feedback + photo is coming soon!
 
I'll keep everything for a fresh thread...

Adrian, thanks for posting those links, very interesting.  
I haven't seen many Alembic 3 Pickups versions, they look amazing.