Thicker walls for more thermal mass?

[diulin]

I'm well into the process of building my first pizza oven. It's a half-barrel design with a brick "house" around it. The plan is to fill the "house" around the arch with perlite. Now I'm wondering if, before I do that, it would be worth adding an inch or two of mortar/Portland mix (a thick parge) or maybe mix in perlite with that in order to create more themal mass. I'm not using a ceramic wool blanket, because the perlite seemed like a cheaper way to get comparable insulation. Please post any suggestions. I feel sometimes like I am in way over my head and just to remind myself that that's probably how most people feel at this stage. Thanks