I need some help- I am trying to create a part in sheet metal- I was going to use a Loft and then shell and convert to sheet metal and maybe a forming tool, but am having trouble with the forming tools...  

This is the part I am trying to make, the top cap- so far I created a loft using a small square with chamfered corners and then offset a new sketch on a plane 3 inches away.  Any help on how to make this would be appreciated.