Janet . This a good one. What must happen is you have to be able to split your routine to fit the size of the floor or the number on the floor.. Michael Barr put out a tape which covered this problem in the International Style Waltz. I think on a crowded floor, with that many people on the floor. Those who learn a routine which starts at A and goes to Z are at a disadvantage. The dancers who learn a group preferably eight bars. Then a few more also about eight bars. Will be able to switch their groups around if needed. Or leave some out. This has been on before . I have a tape of a still top Professional on a very crowded floor at Blackpool. Over twelve bars of music he did the same group three times, the camera stayed on him the whole time. And again in slow motion. If you have a group that you do well then repeat it. A judge can't look at you for more than a few seconds with eighteen on the floor that gives a judge less than five seconds per couple.
Myself I have a few pet steps that I can use if I need to get out of trouble. In the Waltz a Travelling Contra. A Chasse. I like after that a Curving Feather and an Open Impetus and then whatever. What is of prime importance on a crowded floor, keep a good posture all the time. That sometimes is all you need do on that crowded floor to get a few ticks on that card. Trying to do too much can be a disaster.