Here in Orlando, its one the highest earning spots on both twilight and midnight. I get near 100$ more then the chargers, sort, unload and many others. We get more hours then any, except drivers and 22.3.
As for getting onto the preload. Shouldnt be too hard of a request. Preload has a huge turn over rate through out the country. They are always looking and open to people going preload. But be warned, if you turn out good or great at it, it will be hard for them to let you go elsewhere if you start hating the job. Preload is a death sentence.
Edit: its hard, also, for them to let you go because you do earn a skill dollar raise after a period of time while preloading. They see it as, you got the raise, you're stuck here and will never let you go.