I tried both the Hyperlite 3400 and the Mariposa packs. The Mariposa effectively doesn’t have load lifters that help at all. The Mariposa also has a very thick back padded panel, which all it does is push the backpack away from your body, forcing your upper body to work harder to keep it upright. The hip belt is pretty sloppy IMO and the pack relies on putting all the weight into your lower back and shoulders than out towards your hips. Some people might prefer that, but I found it terrible.
I personally think the Hyperlite packs are some of the most overrated items that are often thought of as high-end. Their shoulder straps are a complete joke. It’s not like the pack would even weigh more if they just changed the shoulder straps to be even the slightest bit ergonomic. They should be backpacks designed as dry bags, not dry bags designed as backpacks.
If the Hyperlite 3400 pack’s hip belt felt fine, which it is actually a very well built belt, then you might want to look into trying to add your own load lifters to your existing pack, or look into modifying the shoulder straps to fit you better.