You might be right. Aside from the grooves, all the VCores have noticeably thicker-beamed throats, in the plane of the stringbed, compared to Yonex's previous lines. Also, the introduction of the 3D Vector shaft coincided with an almost wholesale switch from 16x19 to 16x20. I wonder if they felt the new shafts granted enough spin to warrant prioritizing control over spin with the string pattern. Hmm, I've been looking at some older Yonex frames lately. Read a lot of reviews about the RDS 002 Tour, which looks very nice on paper, but quite a few posters described it as erratic on groundies. I wonder if it shared the 001 MP's torsional instability. Recently I've been leaning toward thinking that frame stiffness is relatively unimportant, in any plane. Maybe I'm wrong. Yonex certainly seems to be beefing up their beams, across their entire line, and from tip to butt.