Upper body Chest, Arms, Shoulders
3 day a week
[lower body stuff]
1 day [/quote]
Right off the bat, the fact that you’re okay with this blatant overemphasis (or really, de-emphasis) is a bag sign.
Lots of useful info so far. I’ll just add that, if you want to add “as much mass as possible”, you need to think about nutrition at least as much, if not more, than you think about training.
Last thing, regarding “Is My Upper/Lower Split the Best It Can Be?”:
Very rarely is anyone’s plan “the best it can be.” You’re always going to adjust, adapt, tweak, and fine-tune as you go along, month to month, week to week, sometimes session to session. Definitely have a more general bigger picture plan in place, but adaptability is much more important than trying to lock in “the perfect routine”.