DO NOT mount them (strobes) on the bottom.
I purchased one and mounted it to my Polar Pro landing gear which placed it next to the sensors.
It was the shortest and most terrifying 30 second flight I had. As soon as it launched it couldn't see the ground and the Spark couldn't figure out what altitude it was at so I brought it down with a very hard landing.
I don't think the light will affect the IR but it definitely affected the Visual Sensor.
I have since relocated it to the rear arm on the bottom and it seems to be far enough away from the sensors as I haven't had a problem yet.
Mounting on the bottom allows me to see it in flight regardless of orientation but I also have a mount on the back of the arm that I can use for directional information.
I'll eventually get another one of a different color to mount on the front arm so I can tell if the Spark is coming or going.
I used that 3m plastic lock to secure the strobe.
