I am trying to convert the attached file from a lofted solid to a sheet metal part.  Seems like this should be pretty simple, however, I've failed at all attempts.  What am I doing wrong?  I tried to convert, but the model is missing a transition radius from the top to the sides, I tried to create curved surfaces which worked well, but I could not join the 5 sheet metal parts into one part that can be flattened. 

Any help would be greatly appreciated,

thank you

Steve