Firebox Questions

Hello Gentlemen, I'm in the process of the planning stage for a reverse flow smoker. I've got the tank and have mocked up a drawing to show how I think the build will go.
My main concern is my Firebox. The tank is relatively thin metal. I know it will be hard to hold heat in the chamber. Should I beef up the reverse flow plate by using 1/8” metal or more. Or should I make the fire box larger than 1/3 the chamber size to keep the heat going?

According to pit calculators I need a 24” tall x 32” wide x 32” deep. Which will be a little more than 1/3 the size of my tank. I thought I would put 8 total intake holes on the firebox, 4 on each side.
I've included a .pdf attachment of the drawing and I welcome any comments. Thanks.

Wrapping the tank would be quite an endeavor and expensive. I'm conflicted as what to do because I've read where guys have done both. Thinner RF plate due to recovery times and wasting fuel to heat the plate and I've heard folks using thicker plate when they have a thinner cooking chamber. Thinner metal on the plate and cooking chamber could mean less fuel consumption and smaller fires b/c it would get hotter quicker. The flip side could be more fuel b/c of heat loss.

I think Due to cost I think I'm going to have to use thinner metal on the plate. I'm guessing the tank itself is 12 gauge steel which is a bit less than 1/8" I think.