We are a snowplowing contractor in Grand Rapids, MI. Seems like quite a few contractors have gone to the poly set up. I happen to like the steel. We use the Boss 8' straight plows. We did have a poly sheet installed on the plow that is on our '91 CTD. An 8' piece of mini-c channel is welded onto the face of the blade immediately above the cutting edge. The poly is inserted into the mini-c, then clamped to conform to the curve of the plow. Bolts are then used along the top edge of the poly to hold in place. Many contractors used this system before the poly plows were introduced to the market. The poly face on the steel works well, and I've found it to be particularly useful for re-facing older plows, rather than sand blasting and repainting.
Andy