Look what I just got in the post

Yes, but they won't fit your road bike. I considered both EE and M5 for my weight weenie bike, and eventually rejected both as too ugly, although all reports suggest that they are probably the top two among WW brakes for stopping.
Anyway, it's all about aero for brakes these days, so at some point this year I'll be shelling out for one of these:

Their tests say they're about the same aerodynamically as a centre-pull. I'm guessing they work much better though. $200 USD for a front only. $375 for both.

http://reviews.roadbikereview.com/simkins-egg-brake-pro-review/1

How much distance will they get me in 24hr? :)

"the egg brake was shown to save 3 watts of power over their test course. By Thomas’ calculations, the rule of thumb is that a reduction of 10 watts equates to 1 second per kilometer of time savings. If the Egg Brake saves 3 watts of power, this means that over a flat 40KM course, the brakes will save 12 seconds. And over an Ironman distance of 112 miles, that savings goes to 54 seconds."