Well said John, thanks for clarifying those points.

The size of the pack will depend on the size (and fitness) of the dog. I wouldn't use one on a small dog, however a lab or shepherd sized dog can easily handle a few days food and their little extras on their back.

I suspect that before we started to interfere with the breeding of dogs the rear dew claws may have been very useful, my dog uses his front ones for everything too.