It is no question of what I think. It is physics/mechanics. You want a system with equal distribution of forces, so there are no moments causing the system to rotate. You only have to look at the pitch axis, because your copter is symmetric to the roll axis. Your copter can lift twice as much at the front (4 motors) than at the rear (2 motors), so to make the system balance you need to put more weight to the front of the copter. And this means the CoG/FC should be at 1/3 (2/6) aft from a line between the front motors.
The CoT will be at this point, you have to make sure to put the CoG and the FC in the same spot. Otherwise (CoG != CoT) the copter will have a tendency to pitch up/down while ascending/descending. Placing the FC away from the CoG in any direction will cause the accelerometers to read pitch/roll movements as up/down movements, causing problems in all flightmodes requiring alt hold.
The distance between the front motors is irrelevant for this problem.