Not sure if this has been answered before, but I just bought a bass with two J pickups that I want to replace with Entwistle JBXs. Does the size of the pickup have to match exactly, or just the mounting screws? The existing neck pickup, for example, is 90mm by 17mm. The Entwistle JBX neck pickup is 92mm x 18.7mm. I haven't taken the screws out yet, but it looks like the mounting ears and screw holes will line up, but the fit of the pickup in the cavity might be tight. Does that matter? Is it a matter of "if it fits, it sits"? Or do I need to find J's that are the exact size in every dimension?