Working pack dog cert - Anyone trying it?

Around a year ago, I ran onto the SHCA "Working Pack Dog" certification. Its open to alternative registrations (adopted him from shelter.) And I hike a lot with my sibe. It sounded like a fun thing to do, just as a goal/challenge to get us out on more adventures. We've been training up with a pack this past winter. It's great! He can carry all his things, and useful stuff that we use while hiking. All accessible right beside me. However- for WPD, he's supposed to start at 25% of his weight (finish >=10%). I'm realizing, that that's actually pretty hard to do. Just to dream up enough useful weight, that fits in the pack, to get to ~13lbs. I can easily get to 10ish, for a multi-day hike, though that's carrying some water we wouldn't technically need, in the CO rockies. If anyone has done this, do you have any suggestions for what to pack, to start at the required weight, without just loading a pool worth of water?