The lavastone is a compete game changer with offsets smokers and Kamado Joes alike.
In an offset smoker is can be mounted at the cook chamber end with the fire box, normally the searing heat coming from the firebox means you need a complicated baffles system to even temperatures, not anymore. The stone dissipates the high heat through it and sends the rest of the heat further down the cook chamber, simply play with the position of it and you can get the cook chamber within 10 degrees left to right.
It fits equally well in the Kamado Joe Classic, we find the divide and conquer system is good, but can choke the air flow down a bit too much, leading to wood chunks not burning quite as well and producing white smoke. The lava stone creates a bit more airflow, wood chunks ignite perfectly and you get clean blue smoke throughout your cook.
It also enables you to run your Kamado at a slightly higher temperature but the meat always stays protected by this thick stone, the meat cooks quickly and evenly.