Sorry but that's complete BS. I've strung plenty of Radicals with no problem whatsoever. I simply mount the frame firmly, make sure it's secure and string the racquet. I've never purposely "stretched" a frame. Obviously, you didn't use the mounting on the KM well.
"The problem here is either the mounting system used, or the way in which the frame was mounted.". End of story. Klippermate knows it happens.. they gave me the fix... Stretch the frame. Their head tech gave me the advice.