You should be able to put a bend with a large radius in you pcb. I think, however that you may need to have short flat sections at the end of the bends to give flat geometry for unbending. I'm not too sure on this one though and I can't try it as I don't currnetly have access to a sheetmetal lisense.
When you create your bend, choose "roll" rather than "angle". Then when you sketch the bend line, just "use edge" on the end of your PCB you would like to remain fixed. Create the bend on the PCB side of the edge and let the other side stay fixed. Use the tube radius as your bend radius. ProE will create a constant radius bend extending for the entire part. I hope this is what you want.