Since the 12" PowerBook ships with either a Combo drive or SuperDrive, you may want to specify which one you're talking about.
But the fact is, no mainstream Mac burning software will overburn. I think it can be done via the command line, and there might be some Aqua front-ends to the command line utility.
That said, why bother? Overburning further reduces data integrity (those damned 700MB discs are bad enough as it is), and isn't fully compatible.
tooki