I just bought my first pair of field boots. I am 5'11" tall but bought regular height field boots based on the measurements in the catalog. They have arrived and I am not sure that they fit. They fit well in the foot and calf, but they are loose around the ankle and they are already below my knee (just below but below none the less) in the front and at the bend of my knee in the back. Should I return them for the tall height? How loose are they supposed to be in the ankle? They are the Ariat Select Zip Field Boots. Any advice you can offer would be greatly appreciated.