4x4 with a 2x4 ridge line is doable, rope ridgeline is more common for temporary structures. look to telephone poles they use tension lines in multiple directions like circus tents, as far as the cover goes heading down to the ground waste space but i would do it too although three tarps not one big one so you're shingling with tarps should increase air flow and moisture control.
Bedouins are masters at tent erection for high heat.