Precision Landing with OpenMV

I am trying to achieve precision landing of quadcopter over an april tag of size 1mx1m. I am using openmv H7 hardware with the default camera and its example code which send landing_target mavlink message. I am setting PLAND_TYPE = 1 and PLAND_ENABLED = 1.
The issue is that the drone detects the April Tag at a height of 4-5 m and stops detecting it at an height of 1 m. But the suggestions given in the landing_target, the drone is not following and landing on the April tag. I want to understand should I place the openMV along the head of the drone or across it. Also how is the “CAM_POS” Parameter used in this case.
Following is the link of the openmv example code: