I can't tighten the buckles of my full tilt boots enough to be tight enough for me. The middle buckle which is the most important is completely useless in my boots. Obviously I don't want to buy new boots so I'm about to buy new shorter cables but I don't know which size. The place where I'm going to buy from only has sizes M and L. I have no idea what lenght those are. My boot size is 26,5. Any help is appreciated.