I first tried the HARD springs which were too heavy but the MEDIUMS were just right. The springs are a little difficult to fit, but once you establish a technique it is fairly straight forward. Support the TX on some foam and remove the back cover. Back the tension screw off as far as possible. Remove the original spring then lift the upper arm and hold it in position with some wire to improve access. Use bent long nose pliers to attach the lower loop then tension the spring using fishing line through the upper loop and hook it onto the upper arm. Set the tension screw to give the required stick feel.