Frog users may want to check out the latest Alpine Karst (2006) for an excellent article by Australia's Al Warild. He describes his personal system in great detail and offers several innovative, positive ideas for making the system safe and lightweight.
Once again, I went down in the basement and tinkered with my own Frog rig, now on it's 36th or so modification.
The link for ordering Alpine Karst is under "publications" on this board.
Doc K