The safest thing is to do is know your weight and Va at that weight. Fly at Va and the worst that can happen is a stall which can be recovered by unloading the wings in the standard fashion. At Va you can move ONE control to full deflection without overstressing the airframe You have a 50% margin on top of the certified "g" limits. As John Farley says at the high speed end there is only 5 to 10% margin above Vne and you are almost certain to bend the airframe. The certification is based on aluminium deformation characteristics. Beyond that velocity is unknown flight path response to control input -probably not linear and likely flutter and loss of major components. I would rather carry out a stall recovery at Va than face an increasingly high speed dive well beyond MMo/Vmo.