I balanced an EX1 to a 7D on the shoot I'm working on now. I found it easier to first get the EX1 to the look I want and then play with the gamma curves on the 7D to match the EX1's picture. I also shot the 7D a little flat with less saturation so I could pull color easier in post to match the EX1.
Not sure exactly what to do with the HVX, but I would imagine the process is about the same. Also, make sure you white balance them before you color match and on set before you shoot.