Nuthin' wrong with eggnog!
I took the A30 to Ecuador this past autumn. When I was moving through the airport, on the train, etc, I had it in backpack mode for handsfree ease. I left the absolute strap attached, but under the fastened grab handles.
When the bag was going to be stowed in the below bins of a bus or a boat, I zipped away the backpack straps for their safety and carried it that short distance with the absolute strap and/or the grab handles.
When in the same hotel room for several nights, I again kept the straps zipped away and out of my way.
Basically, I use the backpack mode for longer continuous carry and the absolute shoulder strap and/or grab handles for short distance carry and when I'm worried the backpack straps will catch on something.
Hope that helps, if not, add more eggnog!
Cheers!