OK, so after thinking about ways to put maximum force on the seatpost, it occurred to me that intense twisting might not be ideal for this very light frame. It's a nice seatpost, but not worth risking damage to the frame.

Looking at pictures of the fluted Dura-Ace, I think it has fairly thin walls and is only inserted about 6-7 cm. It should be fairly easily to jailbreak it by cutting off the post and inserting a hacksaw blade into the tube.

Any thoughts? Once I cut the seatpost I will be committed since there will be nothing left to grab onto and twist.