I found a solution to resolve the bouncing when the copter autoland. I set my landing speed to 90 from the default 50 m/s. No bouncing when it autolands, only thing the landing is a little hush. I tried any value below 90 the coptor will bounce when land.
My quad configuration is Arducoptor 3.1.5 firmware, Flip 360 frame, APM 2.6 with external Ublox GPS and compass, sunnysky 980kv motor, Afro 12a ESC and 8x5 SF props. FPV 200mW VTx and a SJ4000 as FPV camera.