Well, Jaco's tone is pretty much based on the idea of roundwounds on a fretless Jazz, with a marine epoxy coating on the fingerboard (so as to prevent the rounds from chewing it up). Different world altogether from Ben's flats-on-a-fretted-Jazz sound.
Sounds like you need two basses

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"Mama" Dave Muscato
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www.MamaDave.com)
Ristola 6er/MTD Artist 5er/Ibanez 6er fretless/Line 6 Variax 5er
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