Batard Blowout - Underproofing?
Maybe someone can help me with a problem I have been having with my batards (and to a lesser exten with boules). Recently, during oven spring my bread has been expanding to such a degree that it spills out from the docking and frequently tears the corners of the seams, making for an unsightly loaf. The bread tastes delicious and I am really happy with the crumb. There is a nice, airy matrix of holes through the loaf and there isn't a ring of dough around the edge (this one is actually a little more dense than my others because it is 1/3 wheat flour).
Is this a sign of underproofing, or is there something else going on? Is it my batard shaping method? Is there too much surface tension from the final shaping?
To give a little background, I have recently been using a high hydration, semi-no-knead bread recipe (though I have had this problem with batards I have made with conventional recipes that started from a biga and with the Peter Reinhart no-knead recipe, among others). The recipe originated with Jim Lahey and Mark Bittman, but was adapted by Kenji at Cook's Illustrated and called "No Knead 2.0". You can find the recipe below, among other places: http://kitchenmusings.com/2007/12/beer-and-the-no.html 
I have been doing 12 hours of bulk fermentation, 30m bench rest, 90m final rise. Is the final rise not long enough? I was thinking about increasing it by a half an hour the next few times I bake to see what happens.
Anyway, I would really appreciate some guidance and your hypotheses.