I think 18 pounds of thrust will fly something alot heavier than 30 pounds!!
I noticed you are in Fairfield, CA. We have another Aero Design competition in Van Nuys on April 25 and 26 at Apollo Field. We have an East and West competition due to the number of teams wanting to participate. Heck...we even have to turn teams away this year. At West, teams will be coming from Poland, Egypt, India, Mexico, Canada, UK, China and of course from the US. It is really interesting to watch. Just grab a suitcase and make a weekend of it.
http://students.sae.org/cds/aerodesign/west/