Just strung my new YT Prestiges and no problems at all with head distortion. I even compared the first racquet I strung with another one that was still unstrungs, and no distortion at all.
I have a Gamma X6-FC, 6 point mounting.
I also already strung a YT prestige Mid and another YT Prestige MP and no problems as well.
3 matched Yonex Ai100 - B5E x Focus Hex 1.18