I always thought that many speed limits were the limits at which significant damage to the structure could start to occur - clearly structural failure rarely happens immediately at any operational speed, and flying up to published limits would not break the aircraft at that point in time, but result in many structural repairs to prevent eventual failure at a later date under normal operating conditions??
nano404 - 530mph at 100' will result in an excessive indicated airspeed, well above the limit: the cruise speed is, of course, at altitude where the air is far thinner and less stressful on the airframe.