Looking great there, Nate! Really good, man, that's awesome!!!
I like those pocket joints... gonna get one of those tools myself one of these days....
I'm not sure about anything thin you can put around it for strength. You might want to just use the rest of the build for that.
I'd worry about that chipboard wall. Covering it is a good idea, but I'd still leave an air gap between that and your heat. I'd love to see a wood box holding everything together on one of these builds but you might worry about heat on that, too. Especially with an 8" system. Oddmar used wood and it seems to work great for him- so check him out for some tips. I love wood, though... could be really gorgeous. Earth is non-flammable though and more forgiving!
"Knowledge is power. Arm yourself."