Guys, forgive me if I am on a tear. I gave up the series parallel idea for the SG because the pups had single conductors and no separate case ground. This DC30 does have that. I looked at JohnH's 2nd module for the S/P implementation but its not working for me. I am sure I have some error here, but I cannot figure it. I used a DPDT one side as I did not have the SPDT that Newey Suggested.
JohnH's idea switches the "ground" (what Dano calls "neutral") wire of the neck pup onto the "hot" of the bridge to make the series connection. With the switch set to "series", you get series with the 3-wayswitch flipped to the bridge neck setting, and bridge pup only in the other two settings.
I took the liberty of modifying your diagram. I used one-half of a DPDT, as you indicated. I think this has got it, but let's let John look at it first.
Neweys version looks good to me. I assume red to ground and black to hot is OK? no reason why not except red is a hotter colour.
One small point of correction, to use that set up in series, you flick the toggle to the neck position, and the other two settings will give bridge.
Thats how I have my LP, thinking that having series and bridge would be the most useful two choices once the series switch is set (which is on the rear of the guitar in my case, so not accessible mid-song). But having had it now for a couple of yaers, I think I might chnage it to hav the neck as the single option - since I'm more likely to use neck as a rythym setting, then series for lead. I mention that in case youd like to think about a similar choice in your case.
The other version of this switching that I use in some designs, is to fully overide the toggle in series mode. This may be better if the S/P switch is accessible, so you set whatever normal setting you like on the toggle, then operate the S/P switch and it always goes to series. This would use the other half of the switch, and the diagram could be adapted.
Ang - how is your latest drawing intended to operate? I havent cjecked it.
The second diagram you posted, the one "from the internet" will also work. In that diagram, as JohnH mentioned, the series setting overrides the 3-way toggle. You're in series regardless of where the three-way is set.
Just "completing the thought" here for the next guy who comes along wanting this.