I have the same AS..........
and the same problem. I am wondering how you would mount the slides?
My battery is "sitting" on a wooden frame that straddles the plumbing lines. The base of the vanity is behind the battery. The vanity is certainly not stout enough to support the battery especially extended on slides.
This one is up for consideration. Anyone with rear compartment and battery stowed in this location, please shoot some ideas and lets see what we can come up with.