You have the bike, so why don't you measure it for yourself? A piece of string and a ruler will do it.

There's really no need for it to be as long as the one on the Jeunet above. The hanger will never get closer to the seat tube, only farther away. I've found that centerpulls are not very sensitive to changes in straddle cable length, in spite of what some people have posted in this forum.