Add strap reinforcement in the form of cordura backing sewn through the pack and the straps
Widen the belt with a wedge-shaped piece of cordura.
It's still too big.
If you can sew, it's no biggee, if you can't - get a different pack.
Just buy the Jam instead of the gust. its 20oz., a bit smaller but more technical. More technical in that it has side compression straps, water bottle holders and is hydration compatible. My only concern for you is it might be a little small. Check it out. Quality pack in my opinion.