If you coil it, you will lose range. Back in the day we used this trick to hide an antenna under a wide oval body. Cut a strip of lexan about the size of a ruler. Put holes on the outside edges in a diagonal pattern, and string the antenna through the holes. Bend the bottom in a way where it can be bolted or servo-taped to the chassis somewhere, and this will allow a full length antenna to fit under a body. I attached a pic of what it would look like. Or you could just buy a 2.4 ghz system. The antennas on those are only 6-8 inches long and can easily fit under a body.