Chris: You don't need all that many small lava rocks. They tend to drop down around the burner area and snug up to each other. Thats why they work so well as they hold the heat in as well as inhibit the air flowthrough. My hinged lid Magma model was s*** until I put in the rock. I think the rock will make all of propane units perform better.
Happy Holidays, Chief
Happy Holidays, Chief