I just got the XL BGE. Here's my question. It came with two bags of what look like lava rocks that are not listed in the instructions. The dealer was not much help, but say that they believe the lava rock goes in the fire box and the charcoal itself actually goes in through the vent and sits on the bottom of the BGE. That way, they say, the heat is distributed evenly and there is no direct fire under the meat. Can somebody help. I want to use it Saturday for a BBQ. Thanks folks.