Good plan. I don't own the same species of jackson as Kemi so I don't know their exact growth rate. He just has very mature horns. That's why I thought he was a older.
There is a blog someone put to ether that tracts the weight of theirs as he grew.
https://www.chameleonforums.com/blogs/weight-tracking-on-jackson.2343/ Maybe the info will be of some use to you as yours grows. Size and growth rate can vary by individual even among clutch mates.