I also felt whip/flex in the 90k but others don't seem to feel that. You have/had Uberschall F5 didn't you? The 90k has a similar feel to the F5 in my opinion.
Yeah F5 has a whippy feel, but feels totally different in the hitting feel. I see how I feel after a couple of sessions. Didn't change rackets in the whole session and for someone that changes often... That's a good sign. Sent from my MI 8 using Tapatalk