Backpack for Dogs

I’m anxiously waiting for Doggy’s backpack (Singletrack Pack by Ruffwear, again free advertisement to Mr. Ruff), if there’s a thing I like are backpacks and the one that I ordered for Doggy is the same color as my favorite. More than anxious I’m curious to see how Doggy manages to have something on top of him. I like to take Doggy on hikes, long hikes, I carry my water and his, but he drinks much more than me so I decided to buy him a backpack for him to carry his own water and my keys. So far all I’ve read are good reviews, not a single complain about the backpack/dog relationship, people complain about the buckle being plastic but that’s about it. Back in the old days Doggy’s ancestors were used to pull fishing boats to shore and to retrieve nets and fish from the sea, they are really strong. Doggy’s family line have been exclusively working dogs, shepherds and also rescue dogs working for the fire department and sniffing dogs working with the police department. Doggy since the day I got it has shown traces of those behaviors, you give him something to carry around and he’s a happy dog, sent him to find something around the house and there he goes, gets extremely frustrated when he doesn’t find it, he cries lol. So I guess a back pack won’t be much of deal for his body, he’s really strong, of course he won’t be carrying me(no yet) but I’ll get him used to it little by little. In some places I’ve read that they can carry up to 20% of their weight, honestly I have no clue, I’ll ask the vet and breeder to see what they have to say about it. Have any of you had any experience with dogs and backpacks?