My old tiercel hybrid (18th season) can take his off the same as Ray's. And, yes I am using the proper Micro-medium tail pieces. He only does it at the beginning of the season when he isn't use to wearing it. He takes it off at home while sitting on the block. My solution is to bend the spring. This photo shows what it looks like after bending.
Doing this makes it impossible for him to remove. Unfortunately the only way for me to remove it is to cut the spring. I fly him with the bent spring for the first couple weeks of the season, and when I needed to replace the battery I cut the spring, and replace it with a normal one. By then he is use to wearing it again and no longer takes it off. He has started the season this way for the last five or six years. It's a little inconvenient having to cut it off and get a new spring each year, but it's a small price to pay, because in my opinion the micro on the tail is an almost perfect backup transmitter for large falcons. None of my other birds, including my current gyrkin have been able to take them off.
Actually Robert if you wanted to make it a perfect backup transmitter for large falcons you could design a new case with bigger post so it could use the larger springs. It would make the transmitter a tad heavier, but it would still be more than light enough for use on large falcons. I don't know what this would take on your end, or if enough people would buy them to make it worth it. I know I would buy at least one.