You should SDC to BOS-LAX-SFO, and then when you get to LAX, SDC to a later flight, and then a later flight, etc., as fare classes open up. You should be able to push your flight back indefinitely as long as the new fare classes are available (may be a bit difficult to push it back to the next day though because fare classes don't level out until about 3 hours before departure and there's generally a lack of flights from LAX-SFO for > 3 hours overnight, but if you got lucky and your fare class was open on just one flight the next day, you can SDC to that and then SDC to another flight closer to your desired departure time as that departure time approaches).