This subject was probably discussed previously, but I've run out of energy searching past threads.
 
Can someone identify what Flim has on his bass between the bridge and the tailpiece?  The tailpiece doesn't look like a stock Alembic either.
 
I was thinking if I put one on my Alembic, I could play just like Jimmie Johnson  
 
Thanks, Dean
 

The tailpiece looks like an Alembic bar instead of the standard bird.  
 
As for what's under the strings, I have no idea-it seems like it could be a mute or something, but as far as what use it would serve behind the bridge, I'm stumped.

VERY beautiful picture BTW!
It illustrates very well the subtle and inspiring style he plays!
 
Paul TBO

I recall something about Jimmy having an aluminum sustain block. That might be what it is.
 
Keith

It's Nice and very interested feature.
 
His aluminum sustain block was reported by Reinier on this thread.
This sustain block is very large, so the block weight is heavy as regular's.
I don't know it's sounds, but I think he wants some additional resonance.
In fact, his original 5 strings bass (76 AC 418) has very large tail piece with impressive sounds.
 
Eiji

Mica or Dave,
 
Can you help us out on this one?  Did the Alembic Crew build it this way, and if so, what is it?
 
Thanks
Dean

I don't know the answer; if Mica sees this thread maybe she'll be able to answer the question.

I'm pretty sure it's just an aluminum block. I'll do a little research and get back with you.