4.25" sag? That sounds like way too much to me. Typically you want 1/3 of your suspension travel as race sag. On our reduced 10" of travel that gives us about 3.3". You would also be looking at having around 1" of static sag.
4+ inches would be for MX bikes and other orange bikes with 12-13 inches of suspension travel.
Just curious have you ever had any problems with the chain slider wearing out?