Sure thing.
Today, I do what yuo said...I cover the top of the kettle pizza extension with heavy duty tinfoil, works awesome. But check out this article...a pizza website. They used a generic Baking Steel Plate, which has awesome heat transfer. This review was so good, that it spurred a demand for Baking Steel inserts. So the Pizza Kettle folks got together with the Baking Steel folks, and you can now gt a Baking Steel plate that is custom cut for the Kettle Pizza.
Enjoy the write-up hare, this was published before there was a Baking Steel custom cut for the Kettle Pizza...
http://slice.seriouseats.com/archiv...e-ultimate-home-pizza-setup.html?ref=obinsite
As to your question about charcoal, I usually use one chock-full chimney of briquettes (I cook on a 22.5, not a 26.75). After dumping the coal, I put the stone on the cooking grate, and cover it. After 15 or 20 minutes of pre-heating, I toss 3 hardwood chunks into the fire. That really stokes up the heat. After letting the chunks burn for 5 minutes, I usually have enough time to cook 3 pizzas before the heat drops significantly. SO yes, I use chunks and charcoal.
With this Baking Steel thing, I expect cooking times of no more than 4 minutes, can't wait to get my hands on it.