How heavy is his Chandler? Seems like people rave about their bats - at $199 I hope so! I'd love to know how close to drop 3 they are.
He swings a 33/30, but he is a very strong kid. He'll also swing a 33 +2 (35 oz) during winter workouts. In my opinion, the weight doesn't matter as much as a kid's mechanics. Your son should swing what he's comfortable with and he can increase it as he gets older and stronger.
He loves the Chandler bat and it has held up as well, or better then the Marucci. In my opinion again, the maples hold up better then the ash bats. When you do order a bat, just specify the length and weight you want. With most bat companies a -3 bat is not a special order.
With B45, like Marucci< which is also a good bat (yellow birch I believe), you can also order a -4 (32/28) without an issue.
I'm not sure if Chandler makes a -4 bat.
With Chandler, you should be able to find one for closer to $175...