I need urgent help with a duster measurment please!!!

This doesn't directly answer your question but it sounds like it will save you A LOT of tedious work.

Why re-invent the wheel when you can buy a quarter panel skin and inner quarter panel extension with the correct curves/creases and sizes? Even if you don't use the entire new quarter skin, it's got the right profile regardless where you cut it to weld into your existing quarter panel.