Z Depth channel and auto gain

Hi, I'm using an Auto Gain node with the Z option on to make my Z channel values manageable, otherwise it's impossible to work with the DepthBlur node.
However, the auto gain changes from frame to frame and it's not consistent, causing the focus to flicker and shift erratically.
Is there another way to do this? The manual Color Gain node doesn't seem to affect the Z channel.
I managed to use a Channel Boolean and put the Z channel into RGB so I can use Color Gain, but then using another Channel Boolean to put it back into the Z channel is not working at all for me, not sure it's a Fusion 8 beta issue or if I'm doing something wrong...
The ideal would be to use some node that would allow me to change the gain of the Z depth channel without all this mess, but I'm open to any other suggestions!
Thanks,
Bruno
However, the auto gain changes from frame to frame and it's not consistent, causing the focus to flicker and shift erratically.
Is there another way to do this? The manual Color Gain node doesn't seem to affect the Z channel.
I managed to use a Channel Boolean and put the Z channel into RGB so I can use Color Gain, but then using another Channel Boolean to put it back into the Z channel is not working at all for me, not sure it's a Fusion 8 beta issue or if I'm doing something wrong...
The ideal would be to use some node that would allow me to change the gain of the Z depth channel without all this mess, but I'm open to any other suggestions!
Thanks,
Bruno