Well, I just disconnected the modulation and soldered a new line directly from the ILDA input pins and plugged that in and gave it less than 5V and measured the output with my power meter. I could have just used a variable power supply of course. The reds and blue drivers had decent linearity between 0.4V and 5V.
It's too bad you aren't going to be at SELEM this year as I could do the work for you in a few minutes.
-David