Have I got a deal for you. It's a completely unused therefore brand new Graphtech Ghost setup for four string bass, using the Hipshot bridge. I want to know what it sounds like but just haven't taken the time to put it into a bass. It takes some work: Excavating under the bridge for the individual peizos (shown in the image) and some electronic work in the cavity. The wire channel from bridge to cavity will likely have to be enlarged too. I'll sell this to you at an absurdly low price for the return assurance that you will follow through and tell us all how your Barker has changed sonically when you're through. I don't think any of this is irreversible, but from what I understand you'll like the new tonal options you'll get. If your Barker 4 has the Hipshot bridge, that part of the project is a cakewalk. The overall work will not be daunting if you have built or rebuilt a bass or done alterations to one. If you're the one, send me a PM or an email and we talk details!