After having seen it, the skids are a blur when you fly regardless of headspeed. I also know your blades are equally tight. At least close enough for government work
Something HAS to be out of balance. Did you try putting your head on a high point balancer?
The torque tube is another good idea. Make sure that the supporting bearing is still supporting it. Might try moving it around too if it can be moved. If the boom is pushed in too much with some designs you can get a skipping rope effect that'll cause vibes as well.