We've tried all kinds of combinations like this in the past and ran into noise and taper issues. Do you need to blend both ways or just roll down some neck pickup?

When using a balance pot, the 2 pu's are in parallel typically (always) if you want relatively even volume all the way through the sweep. When using a balance pot in series it does become a volume knob in a bad way: full center detent = full volume both pu's on. As you sweep to solo the pu's, the volume drops to the exact volume of a parallel solo'd pu. So why do that? The best way imo is a balance pot with the usual parallel wiring, then have a switch or a pull volume knob to go series bypassing the balance pot. Obviously that doesn't give you the ability to sweep 60/40 in series. You may be able to do a series balance pot with resistors.

Yes, its like a twist on the classic 80/20 rule; I tend to spend 80% of my playing time within 20% of the center position. But I definitely use both a "neck favored" and a "bridge favored" sound, so I'd need the blend to do both. I'm thinking a P-tone neck pickup might also make the parallel blend more usable; I like a lot of mids in my tone and right now the neck pickup seems to be contributing a lot of "scoop" to the mix. My bridge PU is a Mach II, so it's got a good bit of snarl on its own. Maybe paired up with a P-Tone neck PU, the blend (with the typical parallel wiring) would keep the mids big and mean sounding. FYI--I'm using a Bourns 500k MN blend, ungrounded and with no master volume control. (I'm not Metallica, I don't turn my bass down. Ha!)

Yes, P-Tone! It will not sound scooped. It sounds so good solo'd [i:2cniiuk4]and[/i:2cniiuk4] in parallel mixed with the MII. I'm blown away by the parallel setting, deep growl. I'm surprised kind of because my experience with 2 MII's in the neck and bridge position, in series on the rotary switch, actually sounded too smoothed out. It was a HUGE sound, but series/series in series was more of a huge reggae sound. The P-Tone is series, so I was expecting the same thing mixed with the MII, huge and maybe too smooth. But it's not the case. There's something about those 2 pu's mixed that is magic. If you haven't installed the blend pot yet, I wouldn't do it until you hear it in the stock Dingwall rotary wiring configuration. The sound is perfect with neck and bridge full on.

Well, some backstory... Back in 2000 or 2001, I bought an '81 G&L L-2000E. The bass had one of the nicest necks I had ever touched, so I bought it as a project, because the onboard electronics were shot. I had owned a newer L-2000 previously, so I was familiar with the electronics scheme in the basses, I just wasn't a huge fan. And once I heard the MFD pickups straight into my amp, I knew I wanted a passive setup in that bass. So, I started brainstorming about how to fill all the holes in the control plate. I ended up with series/parallel switches for each pickup, and a "kill switch" to mute the bass. Controls were blend, a disconnected volume, and tone (in that order because I always used the blend, never used the volume, and rarely used the tone). That bass became my "go to" bass due to the incredible flexibility of that setup. A couple years later, I got my first Dingwall and the G&L stopped being my #1, but I always had that electronics scheme in my head as ideal for me (probably not enough EQ control for most). Fast forward to a year ago, and I was between jobs and had medical bills to pay -- so I sold my beautiful AB2 to cover the medical bills and give me $$ to buy Christmas presents for my daughter. Once I got my tax return I "splurged" and got a used Lakland Skyline 55-01. It was a VERY nice bass and that came with coil-tapped Nordstrand DC's, a blend pot, and a Bartolini NTMB preamp. Between the blend and the coil tapping switches, I never felt the need to touch any of the EQ knobs. And it reminded me of my old L-2000E. Most recently, I got a really good job, found a beautiful AB 1.5 for sale, sold the Lakland (to fund the AB1.5) and have been getting reaquainted with my Dingwall addiction! But I play loud, noisy rock music and find that the parallel-wired FD-3 neck pickup (either soloed or in the parallel blend) is too polite and mid-scooped sounding for my taste. I just want a simple setup with big sound; I'm seriously debating installing a P-Tone, removing the preamp and just having the blend pot and a Tone Styler tone -- I don't see a need to boost the lows or highs on the bass and a passive tone control would give me what I need. Am I crazy?

Check the neck pickup leads. If it's got 4 leads plus a ground, you can re-wire it in series. It will be a little more honky and rude sounding than a P tone but it's a simple and reversable mod and I believe will serve you better for the music you describe.

I'm pretty sure it's just 2 conductors + ground. There was heat shrink tubing around the end of the wire, but if the parallel connection was happening outside the pickup, it'd be happening at the switch, right? On a related topic, I saw a post on TalkBass where using 2 volumes to "feed" the 4-way switch was offered as a possibility. I'm looking to use my blend pot like 2 volume controls, rather than do the "X" wiring across the terminals that makes it function like a blend. Would that be feasible?

I'm thinking of using the "blend" pot like this: http://www.stewmac.com/freeinfo/i-3764/3764_3.gif So that the switch is still in control of how the pickups combine, but the blend just attenuates one or the other pickup...

You are correct, all the rewiring possibilities are external so if its just two wires plus ground, you're stuck for options. Without seeing a drawing of the entire circuit, I can't say for sure if the blend feeding the switch would work or not. My guess is it would kind of work but cause either noise or act like a master volume in some settings. The beauty of doing this kind of thing on your own is that you can make the decision to use a mod even if it doesn't function 100% if it achieves most of your goals. We'd have to reject it for production.