Adding a 2nd roof wouldn't gain much. How would you open the tent?
Fitting The Template (with it's half circular cross section) to the tent won't cut it. What you have is a low box on a tiny ground plane. Consider the techniques used on a box van. A quarter-round is sufficient on the front. That break from the horizontal top to the Template line isn't what you want. Consider Mair:
After the straight section, a curve to the 11° angle, then straight. On the sides and top.