Using crow on landing has negligible effect for light aircraft due to load distribution and pitch up effect. However using crow on landing for high wing loading jets can endanger due to decaying airspeed. After all it turns to be unforgiving aircraft once it reaches to the critical flight envelope.

Hopefully I can also enlighten this for benefit of our jets. The high speed airflow on the top of the wings that produce suction or lift is being interrupted by this crow. It produce high pressure lower speed airflow between the ailerons and the wings. It produces downward push and pitch up moment to the wings. On the otheside since it has the (negative) camber, it accelerates the lower speed high pressure air under the wings. Instead of lift it produces negative lift. However the crow reduces the air separation over the wings at high AoA which is a good advantage. The wings had still the total lift coming from the original fixed camber and AoA. During this process that reduces the resultant lift force, it also shifted the center of pressure forward (closer to CG) that reduces the stability of the plane.