Another option is to let all the air travel to the shallow diffuser which will make a larger open water hole in the ice. IMO larger open water is better than smaller in ice and snow cover.
Bill, with your option I agree on having more open water, but could it not depend on the type of diffuser being used and how much pressure it could handle?
I know I've bled air as Cecil suggests when I've had only one vertex diffuser open as I was under the impression I could damage the membrane.
Just a thought
