Hi Tim,
I have the same setup. I think the high volume helps; however I did put in a small gel pack just in case.
As for the ACC, it depends on how you have set up your camera...
1 - If you are shooting manual on the camera, set the internal strobe to minimum. The ACC isn't used, but the internal discharge is minimized. The strobe is on External Auto or Manual.
2 - If you are shooting in the other modes on the camera, then you need the ACC if you are shooting Manual or External Auto. In this case, the I believe ACC works to minimize the output of the strobe by fooling the internal strobe, but in fact it is possible it is just doing what happens in 3 below...
3 - If you are shooting using s-TTL, then the strobe is mimicking the camera's flash. What is important here is that the internal flash isn't necessarily getting reduced, because if the exposure calls for a large dump of the external strobes, then the internal strobe must do a large dump to trigger this, etc. Generally, this isn't happening, but your battery usage and heat output is certainly higher than in 1.
I have a G9 and Z-240's and suspect that the high internal volume of the housing and the strobes Advanced Cancel Circuitry reducing flash output from the G9 will negate the problem of condensation and therefore any need for silica gel packs. Am I correct?
Thanks for your advice, Tim