Well I went back and tried to fix the problems in the last test flight, which were:
- ESC's not properly calibrated - I was able to get them to calibrate once, but there is something weird about how these speed controls interface with the controller.
- Poor throttle control - It turns out that you should land and take off in "stabilize mode" and I was in "Althold" mode. It took a lot of google searching to stumble across this.
- The receiver refused to work for a while and I don't know why. After plugging and unplugging wires, disassembling the receiver, testing and testing, it started to work again for some unknown reason.
After fixing these issues, I tried the quadcopter with no props and it seemed better. I then lengthened the tethers and ran another test flight shown above, which seems much better.