The length of the cart is set using the side bars (square tubes with the straps). The side bars need to be set so the front straps are just behind the front legs. The longer straps goes under the chest and the shorter strap goes over the shoulders. The side bars should be out as far forward as possible while keeping the straps comfortable behind the front legs. Please ensure the straps are not tight up against the front legs. Please see the next section for balancing the straps and cart in general.
Please put your fingers under the top strap of the cart on the side bars (square tubes), and ensure there is no pressure under the top strap. If you feel any pressure or tightness, you will need to loosen up on the bottom strap and tighten the top strap. Keep doing this until you can feel the pressure alleviated from the top strap.
The straps should never be tight and are just there to balance the front of the cart. When the cart is properly balanced, there should be no pressure under the top strap and the bottom strap should fit like a loose belt. The side bars should be parallel to the ground when finished.