Barry yes the lava rocks act as a heat sink under the element,
then I have a 14" Lodge(Academy) round griddle just above the wood chips as a heat sink
then the commercial cake pan for a water pan sitting on the griddle, it also works as a heat sink
between the 3 heat sinks I get pretty fast heat recovery every time I open the door to add wood.
for years I have been wanting to take it to a welding shop and let them cut a small door in the bottom of the big door just so I can add the wood. one of these days I'll load it up and take it somewhere to get it done, but it does an excellent job now.
what makes the biggest difference is the electric element, it brings the temp right back up to 200° in usually less than 5'mins