Hexacopter Drone Build Suggestions

Hello everyone, just wondering if I could receive some input from someone with experience on the plans that I have for a build. I am building a hexacopter that is outfitted with dual water pumps and reservoirs that will spray cleaning and rinsing solution on camera lenses that are mounted 20m above ground. It is intended to hover in range of the camera lens and spray roughly a distance of 1.5m to its target using the video feed from a camera placed on top of the nozzles for visual reference.

My current setup is:
Pixhawk PX4
PWM to PPM encoder (receiver to PX4)
Divention Devo FE12 transmitter
Divention RX1002 receiver
14.8v 16000mAh Lipo
(6) 4007 740kv motors
Tarrot 680 frame
Wireless telemetry
Twin water pumps with reservoirs (plugged into aux ports of receiver switched by transmitters aux buttons)

My main concern here is keeping the drone stable enough to provide the accuracy needed for this task.

Some of the methods I am currently exploring are:
Sonar detector for displaying distance to target in mission planner
Laser aiming guide to help aid in visual accuracy

Is anyone able to provide some suggestions here to help aid in maintaining the stability of the drone while in flight?