So far it looks like my initial observations are correct. We have had sunny days of about 40-45 degrees F. and calm winds. The oven may get up to 150 degrees at best and I think you need the reflector if you are around the 45th parallel and a higher outside temp. for this oven to cook in the winter. This could be a year round oven for all of you down south without the reflector. I think that could be a big help in the summertime as you wouldn't have to heat up the house using the oven.
I'm still playing with it to get maximum sunlight as I have become very aware of my neighbors trees and my shop blocking sunlight with the sun at a lower angle in winter.
This is a low cost solar oven by design. Kellene in N. Utah has used the Global Sun oven even in winter and had good results, but it also costs twice as much as my Solar oven Sport.