My only thoughts is that I do not want to give up my FM for 2.4. It was cheap and works flawlessly. I looked into 2.4 but when I saw what I would have to spend to switch 4 cars at once I changed my mind really fast.
Anyways, I have such good reception with my FM, that I dont pull out the antenna all the way, just about 12 inches or so. You may be able to do this depending on how big your track is or how far away you want to go.