Rangefinder for slowing down landing in Loiter only

ArduCopter Copter 4.4
1

Hi,

I am using US-D1 radar rangefinder facing down on a big machine where barometers readings get too unstable in ground effect when coming for landing or taking-off.
All flying is done in Loiter. My intention is to use the rangefinder to make every landing soft. This works in Land mode using radar and slowing down the last part of descent but is quite challenging to perform a smooth landing in Loiter.
In Loiter, are the any parameters to set so the rangefinder is only used below certain altitude AGL when detecting the ground closing in, and perhaps below certain horizontal speeds with intention to land?

This sound similar to what I have in mind: Copter: slow the vehicle's decent in Loiter,AltHold,etc when below a configurable alt-above-terrain · Issue #10534 · ArduPilot/ardupilot · GitHub

2 
# Range finder switch height percentage
# Range finder can be used as the primary height source when below this percentage of its maximum
# range (see RNGFNDx_MAX_CM) and the primary height source is Baro or GPS (see EK3_SRCx_POSZ).  This
# feature should not be used for terrain following as it is designed for vertical takeoff and landing
# with climb above the range finder use height before commencing the mission, and with horizontal
# position changes below that height being limited to a flat region around the takeoff and landing
# point.
# Range: -1 70
# Increment: 1
# Units: % (percent)
EK3_RNG_USE_HGT,70.0
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