My wife & I have an A-126. We have a four inch memory foam mattress on top of the seating cushions. The memory foam comes right up under the shelf your referring to. We kept the shelf in place and use it as storage shelving. We installed a cargo net from one end to the other. It works out perfectly. The shelf itself only juts out perhaps 4 inches from the wall. It was never a consideration to remove the shelf & it never interfered with the sleeping arrangements.
Lynn & John
Point Pleasant, NJ
2011 GMC Sierra ExtCab 4x4 Pickup
2012 Rockwood A126