Further to the continued need for old fashioned "mark one eyeball" is recognition that Flarm does not work in all geometrical situations.
I was an unwitting participant in a comp near miss where 2 gliders (both with correctly configured, non stealth set Flarms) failed to detect an imminent collision with the two gliders approaching each other 45 degrees off of head on and one slightly higher than the other. It was over in a matter of seconds, and fortunately we saw each other at the last moment, he pulled and I pushed, and he passed close over me. Neither of our Flarms gave any warning. In our talk about it afterwards we theorized that the carbon underbelly of the higher glider blocked the transmissions between the two Flarm antennas (both of which were mounted on our glare shields). Both Flarms continued to work properly throughout the competition.
ROY