Replying to Boot Flex for Competitive Freestyle Kid

My son is 12, 5', 85lbs and competes in Slopestyle, Big Air and Mogul competitions. He is inverting and is overall a good/aggressive skier. He's kinda in between kids/adult boots. Probably a 25.5 (size 7.5 shoe), but still a relatively small/skinny kid. He's looking at Full Tilt and keeps gravitating towards the 90 flex. Wondering if that's still too much boot? He'd love something with a cuff given the shin bang on the moguls......Any thoughts?