I currently walk my dog for 6 miles, the next day I give him sprint work with a flirt pole, next day I run with him for 15 minutes and the next day sprints again with the flirt pole. It's getting cold and is raining a lot, I'm getting a Carpetmill (not a hard pulling one but smooth turning one, I will be using this mill for his sprinting sessions. Now I'm not sure if to getting an E-mill or Slatmill for when I can't take him on his walks or running session. Which one would ya recomend for this?