Would 1/8" plate be thick enough for the divider plate on a 16"x 42" horizontal patio smoker? Also how high off the bottom of the tank should the divider be, I didn't see this on the calculator?
Are you refering to the reverse flow plate?
If so I would do at a minimum 3/16" as it doesn't take long to heat 1/8" metal up.
Make sure you leave enough room between the RF plate and the fire box opening so any flames do not come in contact with the RF plate as this will give you a hotter temp on the fire box side. Some actually put a plate at the top of the fire box opening, extend it in the chamber and angle it down a little to keep flames from hitting the RF plate. I did this on my 30" x 45" cart model.
Here's what I did.Ok that sounds like a good idea. I'm starting to get my steel together so I'll add a little plate to make a diverter box.