Finished my first run with a 6 man party on normal difficulty and the game balance felt fine to me. Honestly those extra 2 party members weren't even much of a factor when a hasted Karlach was starting almost every battle with 2 frags anyway.
Really baffling that we don't have this option natively. Could even add a disclaimer like "the game is balanced for 4 man parties, don't use this if you care about that" etc.
I care more about adventuring with my pals compared to having balance in this single player game. Obviously not the case for everyone but they can always play the game as intended.
