My saddle bag starts working, and earning it's 10 oz., even before I leave the ground. There is a short loop of shoe lace tied to the ring. The loop is girth hitched to my rope about 2' from the ground. The saddle bag is there to add just a tiny bit of weight so that the rope self-tends while I ascend. Without the weight I'd have to reach down to strip out the loop of rope for the first couple of steps.
When I'm in the tree the saddle bag stays on the rope until I pull it up to change locations. Once I do that I clip it to the back of my saddle so that its handy to use for rope advancements.
It does more than 10 oz. of work for me on every climb.