You are in luck insofar as my having current information about pregnancy duration and scar rupture. I have just finished reading and digesting studies for the VBAC chapter in the forthcoming new edition of  Obstetric Myths Versus Research Realities. I found a systematic review (Lieberman 2001) and three studies that address VBAC after longer pregnancy duration vs. shorter duration. The systematic review did not find a statistically significant (meaning unlikely to be due to chance) increase in scar rupture rate with longer duration. One of the studies did not find a significant increase in scar rupture after taking induction and augmentation (giving oxytocin to make contractions stronger) into account, although there was a slight excess in the group (0.5%) at or beyond 41 wks vs. less than 41 wks. (Coassolo 2005). The other two found an excess that was explained by the excess use of induction in the group with longer pregnancy duration (Hammoud 2004; Zelop 2001). In other words, according to the medical research, you are not at excess risk of scar rupture unless you are induced. I should add as well that studies report a consistent association between inducing VBAC labors and lower VBAC rates, which makes inducing labor batting 0 for 2.

I don't have any data on timing of scar rupture, but you should have the right to make informed decisions about your care, including informed refusal of your care provider's recommendations. And there is much to be said for doing whatever helps maximize your chances for vaginal birth, which, as you have realized, includes feeling relaxed, confident, and encouraged. Maximizing your chance for VBAC minimizes your chance of experiencing the harms associated with any individual cesarean surgery as well as the likelihood of serious harms that escalate with accumulation of cesarean surgeries.

One more idea that is totally in the realm of anecdote and speculation. I have heard that athletes and dancers--women who are used to having exact and complete control over their bodies--may have trouble letting go of control and letting the labor take over, which may interfere with progress. You might look into strategies to help you do this if you think this may be an issue for you. 

-- Henci

Coassolo KM, Stamilio DM, Pare E, et al. Safety and efficacy of vaginal birth after cesarean attempts at or beyond 40 weeks of gestation. Obstet Gynecol 2005;106(4):700-6.

Hammoud A, Hendler I, Gauthier RJ, et al. The effect of gestational age on trial of labor after Cesarean section. J Matern Fetal Neonatal Med 2004;15(3):202-6.

Lieberman E. Risk factors for uterine rupture during a trial of labor after cesarean. Clin Obstet Gynecol 2001;44(3):609-21.

Zelop CM, Shipp TD, Cohen A, et al. Trial of labor after 40 weeks' gestation in women with prior cesarean. Obstet Gynecol 2001;97(3):391-3.