Hi!
A 16x6 will be perfect!
Being a pylon racer at heart for more than 25years, I still find it difficult to land that damn [:@]airplane. Still, my GB is light , weighting just 5kg (5000g). With a 15cc MVVS and 15x4 APC prop it just leaps away at take off.
Differential on the ailerons seems to help slightly !