bulldozer blade vs. ski

Does anyone out there that has designed and/or worked on a sled understand the concept of not having a sharp front edge on the pan of a pulling sled? I've seen a few pans that have a nice front designed like a ski. But....the majority out there have either a square or 45 degree front edge that drags dirt and leaves holes. What gives? It seems pretty much like a no brainer to me or am I missing something? The only thing that I can think of is that a sled designed with a "ski" on the front edge wouldn't be able to stop the big tractors. I would think maybe putting diamond plate steel on the bottom may do it then.

I have found the pulls with a sled that has the "ski" seem to be a lot more consistent and enjoyable to watch and pull in. The sleds with the squared up front edge pull too much dirt, leave huge holes and favor the first tractors in the class. There is much less consistency and "fairness". A good example of what I'm talking about occurred to me/us in the 7,000 farm stock class Sat. night. The three biggest tractors(3020JD,666IH,Allis Chalmers something) that were able to pull in a higher gear had pulls that were nearly double the length of the rest of the field. The reason was simple. They made it past the first hole in the track and the rest of us didn't. I'm not sour grapes here either they would have won either way but it would have been a lot closer. In the one pull I attend every year that has a "ski" design you never see this. There, I'm done venting. Also keep in mind I'm talking dead weight pulling only. What are your guys ideas on this? What are your local sleds like?

Mark