I want to build my own 51 P Bass, butterscotch blonde swamp ash body, maple neck, bakelite pickguard, the old 2 saddle bridge, and so on. I think it would be a nice bass to kick around, and if I buy the body and neck from allparts and do the finishing myself I will have a nice simple instrument (I like things simple, like 1 pickup, etc) to kick around. However, I'm not sure about the pickup. I reckon they pick up a lot of hum, but I dig the style, so a splitcoil is no option. Fralin offers humcancelling 51 P Bass PUs but they are kind of pricey at $140. Are there any alternatives? My next question is regarding the control cavity: is it big enough to house an onboard preamp, 2 stacked pots and a 9v battery? I want to use an onboard preamp with a 3 band eq, but I don't want more than 2 knobs, so I was thinking of using 2 stacked knobs, one for bass and treble, and one for volume and mids. I guess it won't pose a problem enlarging the control cavity underneath the pickguard to house the preamp and battery if necessary, right? I know they went out of fashion lately in favor for passive basses and it might seem odd on a vintage bass replica, but I dig onboard preamps, because I prefer to play directly into the PA whenever possible, and with an onboard preamp I at least have some way of directing my own sound.