FLEX (actually, it's spelt 'FREX' on their name cards). Is a product development company, not an individual person.
Takayuki Nishikawa was the sculptor responisble for the 1/48. Actually, sculptor is the wrong term, as since the 1/48 everthing is done on CAD/CAM and rapid prototyping machines, so maybe calling them 'designer' is more accurate.
I don't know who the individual person or persons are that were resposnisble for the CAD designs of the 1/60 YF-19 and VF-0, but I can try to ask.
Graham