Flatten with Sheet metal question

Hello,

I was wondering if there is a way to flatten this object with sheetmetal and how (ignore the champfers). I can't think of a way to do it and certainly don't know how to model it in sheetmetal. If someone could help me I will be very thankful. I'm leaving the file as well. 

Also I know about the surface flatten but I don't think it will give accurate results