pulling instead of pushing the 7 man sled?

Interesting thought. If you did do that, I would see it fitting into the offseason or early part of the season. As the season progresses, I think it might overstress players because they just don't have the recovery time. I do use a similar method to condition my linemen. When we condition by position, I have linemen push each other for 20 yards (reps are determined by need) then do some 7 yard takeoff and it is great - very oline specific (why would we ever run 40 yard sprints?). I think your sled idea would be better than that.

Something else that our coaching staff has thought of that you could apply deals with our offseason weight program. We have been working on ways to incorporate the toughman concepts. We would have an alternative exercise one day per week (dragging engine blocks or tires, lifting and carrying water loaded weights, holding iron bars at arms length/shoulder height until failure, etc.) for the linemen to experience. Then, at the end of the summer we have a tough man day that the whole team gets to watch and only the linemen can participate in. They think its fun and it helps build some things that are not targeted in the weight room in addition to building unity in that group. Your sled idea might fit here as well. Just make sure they are getting enough recovery time - that is critical.

I am interested to see what other coaches have to say.