The manual directs:
"Use radio packing foam (available at your local hobby dealer) when you install the receiver and battery. With a sharp hobby knife, cut a solid layer of foam the size of the compartment that is in front of the servo tray. Cut out another layer of foam that is identical in size, however, cut an opening in the center of this foam so it will accept the receiver battery pack. Place another solid layer of foam on top of this layer. Cut another layer of foam to accept the receiver. The final layer of foam should be solid."

That seems to be fine to prevent the battery and Rx from sliding around the compartment.
However, I see two problems:
1) Nothing prevents the assembly from moving vertically.
2) There is no freedom to relocate the battery forward or rearward in order to adjust the CG; hence, additional weight needs to be added for balancing.

What I do:
1) Wrap each element individually with foam and rubber bands.
2) Pre-balance the model by moving the battery back or forth.
3) Once the rough location is determined, screw some Velcro strip to the fuselage in a position that keeps the battery from moving under the strong forces of future hard landings, flip over’s, etc. (Some pieces of wood may be necessary, but try making them easily removable rather than glued).
4) Do the same for holding the Rx, but consider placing it out of the way of the battery in case of a crash (on top or behind the battery).
5) Verify that wires are not under stress by being too tight or by vibration from the engine (use some foam to prevent wire movement or oscillation, especially at the points where they enter or leave the battery and Rx and at male-female connectors).