Besides my Nikon SB900s I also the use the new Quadra Hybrids. The new packs are a lot lighter than the older model.
The new Quadra Hybrid AS RX is a compact portable 400 Ws battery flash system for studio and outdoors use.
Complete with fast recycling times, wireless trigger and remote options via the EL-Skyport, the Quadra Hybrid really is a perfect system for anyone who likes to work away from the mains. The latest firmware manages flash power consistency, remote power variation, LED modelling lamp and even more RX features than are currently available on any other unit.
The choice of the battery is up to the user. Lead-Gel batteries for low temperature robustness or Lithium-Ion batteries for lightweight and high flash capacity.
Two heads are available for the RQ system: an A (Action) head for action freezing flash durations and a S (Standard) head for general purpose photography.
For more info check out ORMS. for pricing and stock.
Below are some examples with the Quadras in use.