How to make a piece that is rolled and conical in sheet metal and flatten?

I have attached a file of what I am looking to flatten. I currently work in a fab shop and estimators are coming to me looking for me to quickly flatten pieces like these to give them sizes for plate to order. I have been working on this a couple hours and I have been getting pretty frustrated. A loft bend would work except I would need it to follow a guide curve. I read on one of these forums to just use a surface and thicken, and then convert to sheet metal. I have tried that and I can't get it to work.

I would appreciate any help.

Thanks.

Justin

SolidworksSheet Metal