You're at a disadvantage, but depending on the school, it may not be that large. I know many people who obtained admission last year to some HIGH quality schools -- Yale, Harvard, Penn, etc. after taking the August MCAT and interviewing in Jan/Feb/March. I wouldn't worry about anything right now. Rolling admission schools might be a problem for you, because a lot of them have already written and received letters of intent sufficeth to fill their entering class. Although you'll most likely be competing for spots on waitlists at most of the schools you might interview at, be thankful if you get any interviews. Some people I know who took the April MCAT and applied in June haven't scored any yet.
The way I see it, from now until the end of December is a crucial time for you -- if you get interview offers in that time span, you're in ok shape...if not, time to actualize that contingency plan...
Good luck.
[This message has been edited by Gadfrog (edited 11-15-1999).]