I'll echo gummi on the 22. The stock pan works terrific and although some may have done it, I have never heard of anyone using a different pan altogether in a 22.
Re: the terra cotta, I have never seen the need, especially using a draft controller. When I foil my pan, i leave an air gap underneath or crumple a tiny bit of foil under there. It helps keep the burning doen. Although there is perhaps some utility as a heat sink, my guess is that it is marginal and not using one is one less thing to deal with.