My players beat the Fearful Symmetry pretty easily, but I knew that would happen. The players had a nearly max scan roll, so they new about the self-destruct mechanism and they were going to leave until I mentioned "the Azlantis might have some cool gear..."
The party boarded the Azlanti ship (there's a nice map of the ship in the back cover).
* The Aeon Guard Specialists are no slouches and they have nice armor, weapons and combat skills, so the real trap could be the firefight onboard the enemy vessel.
* The party knew from their way-above-average scan that there were two life signs on board. If you want to make this onboard combat surprisingly challenging, there could just happen to be 1 or 2 SRO crew members (I decided this part of the story didn't need to be extended that much so didn't add the extra challenge to my campaign)
* When the Aeon Guards were about to be beaten (around 10 HP left), they initiated the self destruct. (The Azlantis exchanged code words in their communicators and then typed codes into their forearm computer pads)
* The destruct sequence gave the party 5 rounds to get off the ship, one party member could read the Azlanti language countdown to estimate time left.
* The destruct sequence locks the outer airlock doors, the party unexpectedly has to make a DC 20 computer check to exit (if you want to add tension).
* My group was able to hack the computer to unlock the airlock doors and, since they had such an awesome computer roll, 15 above what they needed, they also reset the timer to give them an extra 6 rounds before detonation (but in no way would I let them deactivate the self destruct). They scrambled to grab a few boxes of mystery loot out of the cargo hold and made it off just in time along with the Aeon Guard bodies and gear.
* The Sunrise Maiden took some serious blast damage for their greed since they cut it down to the wire on the get-away. They got a few very interesting items of moderate value (mostly for story flavor and role play, nothing that breaks game balance)