13x4 sport is too little blade for the YS 63 when using high nitro... you must use the 13x4W at least, however, as Mike points out it depends on the model

The Flip 3D has a fun fly section, and a very forward thick one at that, and so this prop works. It is not so good on the Capiche...

13x6 is better here, and I suspect that the 14x5N will be even better but I have not tried it with this model yet