A few months ago (mabye even last year) Don Szur wrote an outstanding article in Flying Models Magazine. It went into detail on how to construct a winning freestyle with all the elements the judges are looking for, in addition to music selection, maneuver combos and such. One of the things that helped me the most from that article is the simple idea that before you even go to the field, know how you're going to fly your freestyle, including music, maneuvers etc. It's just way too hard to figure it out at the field with a transmitter in your hand - it must be planned out in detail from the start, including the cheoreography, before you actually fly it. There will be areas that just don't work with the music, and that you have to change a little. I know this doesn't directly answer your question but I think it might help you with constructing it. --- Try to find that back issue of Flying Models - Don Szur writes fantastic articles.
take care,
Jon L