I would have to fix it by adjusting the passenger zone numbers
The Excel system you cite appears to be dreadfully cumbersome. One wonders why the operators didn't choose to have the flightcrew just run up a loadsheet on the flightdeck .. ?
as to whether the aircraft would fly ok without the adjustment
As in so many things .. it depends.
In essence, the aircraft, as certificated, is reasonably easy and nice to fly.
If the CG is permitted to move aft, especially, things can get out of hand.
At the aft limit, the aircraft will be compliant with the Design Standards.
As the CG moves outside the aft limit, the static stability reduces. What the pilot finds is that the aircraft (in pitch) becomes progressively twitchier with lesser stick loads causing greater responses to the pitching flight path .. ie the aircraft gets more difficult to fly accurately and the pilot has to spend more of his/her cognitive capability keeping an eye on what's going on. Indeed, the risk of pitching structural overload increases rapidly.
As the CG moves further aft, we move from a condition of static stability to one of static instability. In this situation, the aircraft should be flyable but the workload is extremely high and the pilot techniques required are quite different to those used normally. In general, the typical pilot without flight test knowledge and experience will fail in the task and the aircraft will be lost.
As the CG moves yet further aft, the aircraft moves into a CG situation where it becomes dynamically unstable and beyond the capability of a human pilot .. loss is inevitable.