Gossamer Gear Quiksak for kids

Any thoughts on this pack for an 8 year old slim boy? I got him an REI Flash pack which I had modified with a mesh back pocket and 2 mesh water bottle holders in the sides. Only problem is the pack is too big for him to wear yet. He is 50 inches tall, his torso is about 14 inches his waist is 21 inches and he weighs about 57 pounds.I read that the Quiksak my be good for a child to use. He has all lightweight gear now I need to find a lightweight pack finish him off. Any thoughts? Thanks.