We're to mount amp kicker zx2500

So buddy of mine bought a 2500 kicker and was planning on mounting it on the front of the box! It's a little ranger extended cab with back seats out and custom box with subs facing forward and ports firing up! The baffle holding speakers is a inch and a half thick! He want to mount the amp vertically between the two subs! I told him not good idea cause flex but he seems to think that because baffle is so thick it's not gunna flex?

Thoughts???