I love my Coleman oven.
BB
They are a good bit of kit but are a little small plus do not trust the temperature gauge as its very inaccurate. You will also get heat loss and the stove benfits if you wrap the oven in something like a fire blanket.
Surely it shouldn't be hard to make something similar?
That look pretty good!, is the sheet on the lower shelf a baffle to spread the heat from the stove? Theres something similar in the coleman....