My mach has about 500 miles on it with the stock runners still in good shape. I was surprised the quality of the stockers wasn't bad! Anyway I'm planning a trip to ontario this weekend and I'm sure the trails will be icy. I've had 2 pair of 6" shaper bars with 60 degree carbide sitting on the workbench since the sled was new. I haven't felt the need to change them yet because the stockers have been working pretty good in the corners as long as it's not loose powdery conditions. Should I put both sets of 6" shapers on before I leave for Canada or will that be too much carbide and make the sled darty and hard to turn? Also, I read on here some time ago that some guys run two different size runners on each ski. Does the longer (sharper) carbide go on the inside or outside? Lets here it, what do you guys recommend?