Carl,
While I don't have the regs in front of me, a RTG to put more passengers on would definitely require a call to the dispatcher and departing without it could lead to FAA action against you. Think about it. You put more bodies and weight on the airplane. Your takeoff data is now voided and you would be taking off with invalid numbers. Think the FAA doesn't care about that? We used to have the 1000# slop to cover this, but no more. In the end though, why would you need to know the actual regs wording? Common sense dictates the call. You changed the condition of the original release by returning. CYA at a minimum.