Here's a pic showing the bottom of the Mini SpeedWing. I have all the wiring buried in the foam and then covered with packing tape. The servo control horns stick out less than 1/8" so that isn't a problem. The Battery is velcroed to the bottom of the wing for two purposes. First, so that in the event of a hard crash, the battery ejects and lessens any damage that may occur to the wing because of the weight of the battery. Secondly, to fasilitate cooling of the battery.
In my instructions I tell you that you can cut away some of the ply motor mount once you find the C.G. so that you can insert the battery and have it flush with the bottom. Although this will weaken the keel somewhat. After countless full speed crashes I have yet to strip a gear or break anything with this wing.
"Home of the Mini SpeedWing"