It would be good to do at least the experimental cooking with a digital cooking thermometer. At least something so you can tell what the final temperature is in the product you are cooking. We have one that is like a needle and stick it in when you want to chk the temperature. That though would require unzipping the cover and losing heat. we also have one on a 3 foot cord that you can put the probe end into the oven and leave it The readout stays outside of the oven and the door does not need to be opened to get a reading.
Montezuma is NOT your friend.
Measure the actual temp!!!
Why not soup it up ..... into a convection oven. Add a 4w 12volt computer fan on a small solar panel. If the goal is to get room temp food up to say 165F or 185F, before the sun sets, in an oven that is at best 200-250F then add a fan to decrease the heat up time. Would only work in a unit that had a sealed cover though, like the one being tried above.