Keeping montbretia and mint in check

I have a few bits of montbretia and mint in containers. I'd like to put them in something larger this year, and maybe use them to disguise an ugly retaining wall in my front garden. But, I know that both plants are notorious for spreading all over the place.

I have read that you can plant them in pots sunk into the ground to keep them from taking over, but I'm not clear on a couple of things. First, how deep does the pot need to be? Would having a pot keep too much water in the soil and drown the plant? Our front garden is pretty heavy soil and doesn't really drain that well, so this could be an issue. Second, I wonder if plastic 2-liter bottles with the top and bottom cut off could be used instead of terra cotta pots. I'm envisioning this as a plastic sleeve about 8 inches deep, with an open bottom. Or would the runners be able to "escape" from underneath the bottles and spread out anyway? Would the plastic break down too quickly to make this worthwhile?