Remember , the bench test is just for release force. It does not measure elasticity/ return to center. I am not aware of any objective evidence to support the old theory (wive’s tale?) of it being better to be in the middle of the Din range. In fact my experience is that it performs better - elasticity/return to center wise without unnecessary release - when you are running on the low end of the din range since the spring is less compressed and has more “spring” force to stop it going over center and releasing from a momentary shock whereas a cranked up spring has less reange of motion left and is more likely to release. As has been pointed out elsewhere typically above 12/13 din the design and materials usually change. There are some exceptions such as marker xcomp and Xcel where the 12 and 16 are the same and the more metal/stronger version starts at 18