I have been working with one of my customers on volume issues with the G9.
Just to be clear, the G4 mod has the problem with volume being louder when you use the earbuds. It is a matter of impedance and power required. When the earbuds are used you need to run the master comm volume at a much lower level, almost at the bottom.
This is not really a problem with the G4, it is still usable. The difference you notice is when the master volume goes up to compensate for increase in background noise it goes in steps and when you are at a low volume level the steps seem large.
While you can live with it when using a G4 it gets harder when you are using a G9. The volume output of the G9 is higher than the G4 clamp can provide so as a result, it gets harder to live with at the low volume levels of the main control. Sometimes it can get to the point that when you plug in an MP3 player it may not be able to put out enough volume to get "noticed" by the amplifier and you can't hear it.
The solution is to get some resistance in the output to the earbuds. This can be done in 3 ways, either by installing a 56 ohm resistor on the common leg inside the clamp or by installing an inline volume control. If you install a resistor inside the clamp you can no longer plug the speakers back in and use them, the volume will be cut down and you can't hear it.
A simple solution is to get an inline volume control.
I found a source for some short inline controls that seem to work well and are cheap. I picked up a few of them and will pass them along to anyone who gets an earbud mod done for an additional $8. If you have had a mod done in the past just send me an email and I'll send you one for the same price plus postage.
This is what it looks like: