I think after 8+ hours in the smoker, even at low temps, any residual "moisture" that can have cooked out will have. The "moisture" in the final product comes primarily from internal fat and the breakdown of connective tissue into gelatin. Cutting into smaller pieces shouldn't affect this, but it will shorten the total cook time. As a side bonus, it will exponentially increase the surface area of the meat, allowing for more bark and smoke penetration.
**Edit, I should have read all the replies more carefully. HDsmoke said it all before I did.