The two volumes of the stock OLP don't do much. I made mine a single volume and used the second volume as a tone control by adding a capacitor. Then I added a switch to the last hole for series, parallel, and single coil. It's all easy to do except making sure the phasing is correct for the switch. That setup gives the bass a lot more useable tones. Really fat in series, nice slap in parallel, nice clean tones in single coil(with single coil noise). Cost about $5. I think you can get the switching diagrams from the Stewart-Macdonald site or some of the pickup manufacturer sites.
