RE: GWS BB-B
Look at the Aeromicro charts for that motor - I believe you are "under-stressing" it on 2s with those little props. I think you should be running at least an 11x4.7 on that 400C with D-gearing (3:1) - even that is probably pulling no more than 7.5A: - try a GWS HD 11x7 or even a 12x8 GWS HD and see how it flies (your Kokams and the 400C should be able to cope with 10A or more).
Cheers, Phil