I made my own custom body clips from paperclips when I had my RC18T. They worked awesome. One clip for the front, and one for the back. One clip inserted into to posts at a time, and was bent in such a way that you just push it in and then push DOWN, and it "snapped" tight. They worked ten times better than other manufactured clips and they NEVER came off no matter how hard I crashed.

You take a paper clip (you can get them at CVS), and bend it into a "U". Cut length as needed. Bend it so you can enter both body posts at once. Inssert them into the body posts and push it in half way, so there is an even amount of metal on each side. Now take the "U" part and bend it UP about 45-50 degrees. Now push IN and DOWN.

To take it off all you have to do is simply pull it out the same way you put it in. If you do it just right the clip will have the "snapping" effect you're looking for to get a nice tight fit. I hope I explained it well, because purchasing body clips has to be the biggest waste of money I've ever seen. It costs than 1 CENT to make the clips I just described, and they're very durable.