I have done something similar. You have to drop the class after a certain date. This is when the financial aid people take a snapshot of your units for a record, after this date they will no longer check for the rest of that quarter. But since you are required to be a full time student for the whole year they will do a collective check by the end of the year. All you have to do is make up those units (for the class you want to drop in Fall) before the school year ends. You can do this in the Spring, Winter, or Summer quarter you just need to add a class with the equivalent units dropped to make full time status for the whole year. Hope this makes sense.