Just wanted to let folks know that the VAC Motorsports E36/46 under-seat fire extinguisher mount works on either the driver or passenger side in a Z4.
The mount is fixed in position (it doesn't move with the seat) and so with the extinguisher installed you do lose a small amount of forward seat travel, at least with sport seats. I'm 5'11" but have short legs and sit pretty far forward compared to most; I still have two-three inches of forward travel, so shouldn't be a problem for many. Also, not compatible with the first aid box.
Install is easy--remove the nuts holding the seat tracks to the floor in front, loosen the rears, lift the front of the seat and slip the mount over the studs between the carpet and the tracks, and tighten everything up.
I have a 2.5 lb Halotron extinguisher with metal valve and hardware in mine. Warning--it can be hard to find these extinguishers. I tried numerous sources, and all were chronically out of stock. Finally lucked out after a couple months and caught CDOC with one in stock.
I don't really anticipate using the extinguisher during an on-track incident. Rather, it's comforting to have one readily at hand in the paddock or on the street.
http://store.vacmotorsports.com/vac-...e46-p2023.aspx
http://store.cdoc.com/h3r25lbpremium...inguisher.aspx