Always foil my butts once temps hit 165. Not adding any smoke past that point anyway and it always produces a more tender product. Plus, you can save the dripping from the foil for a killer sauce.
And I don't typically have a problem with the bark even when foiling. If it does soften up too much, I just do what FatDaddy and Hoo have suggested and pop it in the chamber unfoiled for 30-45 minutes to firm back up.
Weber Lil Smokie kettle