I've been working with a Haflinger gelding, Gibson, since late December. His owner is training my Haflinger mare to drive while I put saddle miles on Gibson and train him to pack. We have done lots of ponying with a couple of truck tires hanging from his pack saddle, but earlier this week I put the bearproof metal pack panniers on him, loaded each one up with 50 pounds of pelleted feed, horse shoes, and jugs of water to make a rattly racket on his back. The panniers are also a very large and wide load, comparabale to packing a wood stove or wall tent, so the horse learns in a hurry to steer carefully through tight spots on the trail where trees and rocks make a narrow passage.
Gibson had a brief meltdown when I first loaded him up, then settled down and packed along like a good mountain pony. The panniers took a few solid whacks into trees before he learned how much wider he was (and those metal boxes give a much harder whack to the hrose than the rubber tires). We covered 10 miles of trails and logging roads.
I wouldn't put my eggs or china on him, but Gibson could easily get camp and dry goods into the mountains for me. I'll keep packing him when I ride, by summer he should be a pro.