Dan Gibson:The backup generally is run under the inflator hose on doubles. The pics shown indicate just the opposite. I have used Apeks, SP and Atomic and all three configurations work better with the backup under.
I believe Peter Steinhoff posted an article recently on his site where he shows the preferred routing and explains his reasoning which does match what I learned under GUE as well as what I have experienced.
as I have already said, I posted the "costablancascuba" link to show the hose routing for SINGLE tank configuration for the MK25.