I've also now run a few tests now with the 414ex.
Readout noise is 3.91e- better than the advertised 5e-
Gain 0.25 e-/ADU, giving a full well capacity of 16,394 not as good as I thought
From the internet I thought that the 314 CCD had a gain of about 0.25 and that the 414 CCD was more like 0.34. So it looks like my 414 either has an incorrect gain set internally (this would account for both the low readout noise and full well capacity) or the information I found on the web was wrong. As I made the measurements using two different applications, giving consistent values, I'm reasonably certain they are correct.
James