Your statement of 17 gpm @25 psi... I don't see that with the softeners with the Clack WS-1 that I have been selling for over 6 years. And I've sold them on up to 6.5 cuft softeners with many 2.5, 3 and 3.5 cuft softeners. No customer has ever mentioned a pressure loss (or flow) problem. And that includes 2 person showers with up to 6 body sprays. IMO there is something about sizing softeners that you aren't understanding correctly.