I had a HW once - super looking thing in walnut but was very low power ...the spring was 'right' and full length ....but only gave 5ft/lbs . I toyed with all manner of theories , but in this case , I think nlyon may not be sufficient . If you are replaacing spring length by this much I am guessing asI have never tried this [ but have pondered the same myslef ] , possibly a soild bar of ally or brass with a nlyon finish may be better when compressed ?