Here's my cello patch modified to sound more like a double bass being plucked: [MP3]
The pitch correction is way up, but the velocity back-off is also turned up so you can do vibrato without pitch stepping. I didn't listen to a real double bass when making this patch so the decay rate is probably off. I think the noise level and overall harmonics are probably set too high as well. I've got the damping set to damp faster if the hand is farther away, you can hear this more near the end. And you can still play continuously if you're careful passing the knee.
I only spent ~10 minutes on this. Downloaded it into my new patch librarian and saved it to a file (patch stuff is a breeze now).