I just did a butt in my MES 30, took a long time, but had great bark. I foiled it at 190 and brought it up to 210. Didn't interfere with the bark at all. I agree with b-one about cooking on the grate.I actually didn't try it. I want to though...really want to save the bark.
For those if you that have done it, do you have any actuals on cook time? Did you have to reload the charcoal? I usually budget about an hour per pound using the foil.