Chopjock,
That is a pretty limited view of the hazards of "overloading". There is more to it than exceeding engine/gearbox limits.
From my experience, I think the view you express is found in some PPLs (in the UK). Basically, they "weigh" the helicopter by seeing if they can get into a ground effect hover without exceeding engine/gearbox limits. They assume that if they can, then everything is OK - It isn't.
There are a whole bunch of extra considerations that should be considered.