I might be missing something here, but did you shoot a build video? It'll be interesting to see as I just can't seem to find a way to mount the battery and maintain the CoG. Using a 4S 2650, might be too light. but scared that 2 4S 2200s paralelled is too heavy.
I started to shoot a video, but it's just too much for me to wade through editing-wise right now.
The battery is supposed to slide in through the nose-hatch, and slide down under the inlet and under the EDF, essentially in the middle of the wing. That's why the upper surface of the wings are cut back relative to the lower surface. That's your battery compartment. If you need to slide it further aft, you need to cut away more of the wing upper surface, or just fly a little nose-heavy - it actually flies rather well that way.
A 4S 2650 is a decent lightweight battery for the 70mm that I use, but will only last maybe 1.5 to 2 minutes of hard flying. Weight-wise, if you've got a good arm and at least a little headwind, the A-4 will fly on a 4S 6000mAh Graphene battery. It certainly flies 'heavier' (you've got to manage your wing and energy more), but then you've got more flight time to play with.
I usually fly on a single 4500, and set my throttle timer for 4 minutes, based on throttle-percentage. I think 4500 is a nice balance between capacity and weight.
