My answer: Don't do it. If a load cell is specified for 30kg then use it for 30kg max.
If overload is specified to be 200% ... this means 60kg, then the sensor will withstand this mechanically, but this is out of the specified operating area and you have to expect additional measurement errors.
Question: If a bungee rope is specified for 60kg, but your weight is 90kg ... would you use it?
My answer: Don't do it. If a load cell is specified for 30kg then use it for 30kg max.
If overload is specified to be 200% ... this means 60kg, then the sensor will withstand this mechanically, but this is out of the specified operating area and you have to expect additional measurement errors.
on this post, you forget to tell us
How is made the mechanical assembly of your weight sensor
it is a key punckt for all weight scale .
The first step is the mechanical design of the scale , before locking for how to do it with electronics parts.
With only one sensor 30Kg , it is possible to measure up to 100Kpg . ( even loosing a litle bit accuracy and resolution).
maybe your client know more about that, than you ?
If a sensor is declared to 200% overload, 300+% will produce plastic deformation to the sensor and it will be rendered useless. Mechanical construction does not figure anymore.
As per Klaus writing, if your weight is 80kg and you wish to use bungee cord declared to max overload at 60kg, I would encourage you to jump :-D and in the aftermath to hear from you about the adrenalin rush :-D :-D (if you survive).