Packs, including their hip belts, must be designed for some 'normal' shape of body, but of course there really is no such thing, only approximations that are either closer to your own body's shape or further away from it.

I know of no simple, quick or foolproof way to modify a hip belt. Because the Deuter started to feel uncomfortable after 20 minutes, it most likely will repeat that performance out on the trail, too. Because the Aura fit your body more comfortably, that is probably the one that will be most comfortable out on the trail.

Luckily, you won't need to leap around very often with your pack on your back. Mostly you'll just walk. When you do need to leap about, temporarily cinch the belt and straps a bit tighter, then readjust it again when you resume walking.