An 11.7% stout will take awhile to carb if you didn't add any fresh yeast at bottling. My recommendation is to do nothing at all. I bet they will carb given a 65-70F environment and a few extra months. The extra time in the bottle will take the edge of this massive brew and taste better anyway.
I brewed a 12% RIS back in April, and I've drank exactly 1 beer so far. It did carb after 4 weeks, but I added some fresh yeast at bottling. I have my second bottle in the fridge for the next few weeks to enjoy after Christmas. But the bulk of these will be enjoyed this spring and next winter.
Primary #1: Empty #2: Black Currant Wine
Secondary #1: Berry Rhubarb Wine #2: Empty
Kegged: Cascadian Dark Ale
Bottles: Spruced Winter Warmer, Surly Bender clone, Big 50 Barleywine, Framboise Lambic, Dark Belgian Strong, Kicked by a Moose Scotch Ale, Russian Imperial Stout, Sparkling Elderflower Wine, Barolo Wine, On Deck: Orange Pale Ale IV, Hidden Lake Nut Brown, 2H IPA III