I run a non stretch, with the 16T pinion, sped up tail, 4500mah Pulse 6 cell packs, with a receiver pack and a HW 120 V4....I run 1700, 1900, 2100....2100 is a bit too high for the pinion, but I don't run it there that much. I'm easily getting 10 minutes of big air and dabbing into 3D, so light 3D. I'm using an Xnova 4020-1000kv motor.
I chose that setup due to being able to go higher than 6 cell. If I were to do it again, I'd not consider going more then 6 cell, get a different ESC, one with a BEC, as I'm on the heavy side for a 516, 6 pounds, 14 ounces.