Start by making the rub...Combine the brown sugar, paprika, salt and pepper, and rub the mixture over the roast and wrap it tightly in plastic. Refrigerate for at least a few hours but overnight is best.
To make the sauce...combine the vinegar, worcestershire sauce, red pepper flakes, sugar, mustard, garlic powder, and cayenne pepper in a bowl and mix well.
Next, place the quartered onions in the bottom of a crock pot. Place the (unwrapped) roast on top of onions and drizzle most of the vinegar mix over the roast. Save a little bit to add to the shredded meat at the end.
Cover and cook on low for 7 to 8 hours, or high for 4 to 5 hours. (I actually cooked mine for 10 on low because that's what fit in with my work day!)
When your meat is done cooking, remove it and the onions from the crockpot and transfer to a cutting board. Remove skin and fat from the pork. Using two forks pull and shred the pork and top with the remaining vinegar mixture if desired!
I served this with a side of cole slaw and corn on the cob! But the meat would make an excellent pulled pork sandwich as well!
And lucky Truman enjoyed the pork bone...