I've been seeing quite a few triathletes in the fitting studio lately, and many are using a standard road bike, but they want to be set up in "tri position". They already have clip on extensions.  The problem is with the seat tube angle. Even a zero offset seat post and a saddle forward on the rails does not achieve an ideal saddle setback. Too slack. Enter the redshift dual position seat post. This ingenious invention allows for on-the-bike swapping between a road bike seat tube angle and saddle position, and a tri bike seat tube angle and saddle position. If you are not familiar with it, check it out!