In virtually all of the sheet metal parts that we design, we only care about the final dimensions of the part, not what bend radius, k-factor, etc. were used to get it there. With our in-house sheet metal shop we're lucky if they get within .125" of any dimension on the print. With jobs that need more precision, we send them out to a sheet metal fabrication shop and let their engineers change the numbers until they like them.
My curiosity with using equations in SW had more to do with having a parametric sheet metal part that would always be the same height, width, etc. independent of the bend radius or thickness used.
That being said, I don't deal with sheet metal all that much. It only comes up once in a while. I know little to nothing about the art and science that is sheet metal bending.