Sheet metal transition bends

[nickstevens]

I have a question regarding sheet metal. I'm trying to bend half the edge of a piece of sheetmetal so that half of the edge is bent, then there is a transitional bit the the edge becomes straight. I know that I am supposed to use Bend Angle w/Transition but i can't seem to get it to work - i always get the message 'unable to construct feature geometry'. If anyone can shed some light on this i would be very greatful.

Thanks