I have nothing to show for the last couple days of "working" on this project, but at least that doesn't mean I've accomplished nothing. 

One thing I've got pretty well worked out in my head is a different (better?) way of powering the transmitter. The little portable charger thing I'm currently using works, most of the time. If the NRF24L01+ isn't running the power brick just shuts off. I think the circuitry isn't pulling enough current for the brick to believe it's connected to something. So far it's not been an issue when the radio module is on but I'd hate for it to decide mid-flight that the transmitter isn't pulling enough juice. Also, as mentioned in part 6 of the destructions, I can't see how much (or little) charge is left when the case is closed up. Aand I would really like to be able to charge the transmitter without opening the case. Aaand it sure would be great to be able to program the Teensy without opening the case and unplugging the battery. So I think I've decided to go with something like this and a bog-standard lipo battery (kiddo had a 2000mAh one just sitting around). I'll grab a micro-usb breakout board and I should even be able to use the transmitter's original charger hole.

That was the easy part though. Now, I freely admit that the current code (rudRemoteCrazyOnly.ino) is mainly copy-pasted from what I had running a few years ago. And that was largely copy-pasted from other peoples' Crazyflie transmitter projects. There was something in there that didn't make a lot of sense to me: What was RADIO_CHANNEL doing in crtp.header? It turns out that it doesn't belong there at all, instead that part of the header is used to request a specific channel of certain ports (e.g. Logging). It doesn't cause problems so far because the Commander port doesn't have channels. That got me wondering what else I'd missed the last time I'd actually worked on rudRemote. So I've been slogging through documentation and source code, refreshing what I thought I knew about RF24, seeing how much I actually remembered about CRTP (answer: not much), and generally making a plan about how I want to proceed.

At the very least I can say that, as it sits, this project works for one of my goals. I have successfully flown my Crazyflie (much to my wife's dog's chagrin) with a 40 year old transmitter and I crashed ever so slightly less than when I fly it with my phone.