Modified RF Build Opinions

So I'm getting prepping to do my first run at concessions with a small(100ish) cook. To handle that volume I borrowed my Grandpa's smoker, which he and his little brother built ages ago. She's a good old gal, nice and reliable, but like most side fireboxes she has temperature variation problems. Now if things go well with the concessions, I have intentions on building a 500 gallon RF. I'm pretty happy with the way most RF cookers are set up as far as the cooking chamber is concerned, but I got to wondering it it would be possible to build something like my Grandpa's smoker except reverse flow to alleviate those temperature issues. Below are the pictures of his smoker. Now basically what they did was halve an old tank, removed the end caps, and then attached what's basically a large box atop the tank. This allows for there to be not only shelving, but also rods to hang meat. Not sure if it is possible for that much open area, and I would have no clue where to begin doing the math because the large box on top of the tank completely throws the normal calculator. The crappy paint drawing is what my basic thoughts were. In the upper left side of the chamber there would be rods for hanging if the shelves are pulled out on that side. Nothing is to scale on that drawing, just so we're clear.