I started with 35 in the Goruck Bag as it came with a 20lb plate and i stuffed a 15lb dumbbell in there too. The Goruck bag was a gift I would have never bought for myself, but it is a great training tool. I have been using it since late April. My wife has seen how much I've been using it so a 30lb plate showed up the other day so now i have 50lb in plates. It has little pockets inside to hold them and keep them from moving.
This is not intended to be a ad for Goruck products. I would have continued using my MR pack and a bag of landscape stone that I used to get ready for Montana a few years ago. but I really like the new setup.
Other than looking like a weirdo wearing a backpack while mowing, I'm going to continue grabbing some extra exercise when I can. I go on a good walk with the pack once or twice a week(3+ miles) and then use a elliptical 2-3 times during the week. It is working pretty good so far for functional health and fitness.