Mike, as far as the fat cap goes: Personally, I trim almost all the external cap off of Boston butts. Two reasons: First, there's enough internal fat inside a pork butt to keep the meat moist and juicy (plus, brining really helps in that department). Secondly, I don't like all the extra fat in the pulled pork. If the cap is very thick, it won't all render down, and you'll have fat in the pulled pork (more than you should). Plus, the fat cap inhibits brining, and rub affecting the meat itself.
