ROPS Analysis

   Need some help with ROPS analysis and design Criteria  

    I am aware that the (Roll Over Protection Structure) ROPS analysis is an ocean and I have just started to explore it as there is a need of it at my work. As of now, I have more questions and many wrong answers. So kindly bare with me. I will start with a brief introduction of what I know followed  by my question.

    From what I have read so far in the ISO standards I understand that ROPS, in the context of earth moving vehicle's CAB, is a frame specificaly designed not to deflect beyond a limit( which is called DLV : Deflection-Limiting Volume) so as to avoid injuries to the operator sitting in a CAB with his seat belt on, in case of a machine roll over.

   When I think of a ROPS frame that satifies this criteria of the ISO standards, I can imagine  three different designs.

1. The first design can be a frame that is very stiff and hardly deflects any for the given critical LOAD. The operator might experience shock in this case.
   
2. The second design can be a frame that deflects just to an extent that it does not injure the operator.
3. The third design can be a scaled up version of the second design with less stiffness so that it still deflects just to an extent that it does not injure the operator. When compared to second design, the third design will deflect more in the given time period for a given load.

All the 3 designs 1, 2 & 3 satisfy the rops criteria but on what basis do I optimize the design? Is there something like energy absorbtion rate or deflection rate I need to target for to optimize the design?

Any information with regards to my question will be of great help

Thanks in advance

Praveen