I have the same quad with cc3d flight controller....
I once tried a 5000 mah 3cell battery which weighs 450 gms......
....was able to lift at 95% throttle ....landed immediately...motors n esc's were hot like tandoori
...
with a 2600 mah it should be able to lift but will be quite unstable...specially with kk2.1..
my suggestion...don't go over 2200 mah. I.E. 200gm of battery.