Interesting question. I've only cut up boneless pork butts, usually to make buckboard bacon. Earlier this week I picked up a 3.11 lb pork butt that had been sliced horizontally. It contained part of the money muscle. Once again, I'm curing it for buckboard bacon, but that might be a way to do it if you have a band saw to cut through the bone.
Or..........you could pick up a pack of boneless pork shoulder from Costco. It is two boneless butts, usually about 8 lbs each. You could slice it any way you wanted based upon how the bone was removed and how thick you wanted the piece of meat.
I never trim the fat cap on pork butt. It isn't the same kind of hard fat as say a brisket.
Rubs? Here's my current favorite for pork.
Pork Rub
Ingredients
2 Tbs Dark brown sugar
2 Tbs Paprika, sweet or smoked, your preference
1 Tbs Seasoning salt (Old Bay)
1 Tbs Kosher salt
1 Tbs chili powder
1 Tbs dry mustard
1/2 Tbs Fresh-ground black pepper
1/4 tsp ground ginger
Directions
1. Mix all ingredients in the order shown. Stir with a spoon, breaking up any clumps. Store in an airtight container.