Chopjock:
You're way out of your league in terms of talking of limits and designs. There is a maximum weight published in the limitations. Your job is to not exceed it.
Ignorance is not excuse in a court of human law, nor in the court of physical laws.
(I was a certification test pilot for 5 years for Transport Canada, and can testify that there are a myriad of reasons for weight limitations, as well as other limitations.)