I fiberglassed the bottom of the hatch (top of wing inside hatch area) to make it stronger for attaching the Rx and battery (pic 1). Pic 2 shows the Rx antenna attached to a piece of scrap balsa that I hot glued to one of the ribs. I wanted to get it a reasonable ways from the battery so it has less chance of getting shadowed.

Also mounted the charge jack and switch so they are easily accessible from the top of the airplane (pic 3). I glued a piece of 1/32" plywood to the inside to double the balsa where these were installed.