What size bell is recommended after 16kg? Been doing circuits, get ups and one arm swings included so i know i can do those 2 exercises with 16kg. Im gonna do more simple sinister from now on and not sure if i sould go with a 20 or a 24? Moneys tight so id rater not have to buy again very soon but dont know if the jump to 24 is too much. Whats recommended?