Erm, I'm no lighting expert, but if your flash is overpowering the backlight, how are you going to get a backlit effect? Your fill light should be much weaker than the backlight for the backlighting to show..
Jed, care to share the technical details of your shots? I really like the first one..
Err... they're not meant as a trio lah... just whacked together quickly. 3rd sort of represents a different technique of backlighting, and a different effect. Individually it's probably not as impact-strong as the other two.
Actually, it's difficult to meter for the backlighting. If the subject fills the frame then you should be able to expose normally... ie TTL flash metering should do a decent job. Otherwise what you really need to do is not so much meter the flash, but control the amount and quality of flash.