If it isn't with you, it can't save youTM

I always carry my PLB (currently an ACR MicroFix) on my belt. Too often a backpack is lost in the process of getting into the situation you need the PLB to get you out of. A fanny pack would be not quite as secure as on the belt, but would be far better than a backpack.

The PLBs are pretty tough, so padding it to prevent damage in a fall really shouldn't be necessary. OTOH, they are not quite built like a brick, so there's a trade off to be made. I vote for improving the chances it will be with you when you need it.