Not to knife-edge, only to the downwash issue, some figures:

The Integral pattern plane, set up for 100 ft/s (about 70 mph), needs 0.5 degrees decalage if static stability margin is 9.6%, 1.0 degrees if static margin is 30.4% (C/G exactly at 25% MAC). Or an equivalent elevator deflection. In the first case, the stab is still lifting up (Cl 0.03), in the other case it's pushing down (Cl -0.01). At 29% static margin (maybe 27% MAC) stab Cl is zero, but decalage still 1 degree.