Aft CG: the relationship between your aircraft's performance and CG location is simple: by moving your CG forward and aft, you change the amount of tail down force and lift you need for stable flight.
When you create more lift, you create more induced drag, and your performance goes down.

When the Center of gravity is moved to forward limit, this gives us a pitch down moment, this pitch down moment has to be corrected by down deflection of elevator to keep straight and level flight, this down deflection increase the drag, increasing drag reduce the endurance.

The down deflection of the elevator which is used to compensate for the nose heavy moment, is the same deflection we use to pitch up to increase the rate of climb, when part of it is used already for compensation, this result in reduction of climb capability.

When the Center of gravity is moved to aft limit, this makes pitch up moment, which improve the rate of climb and decrease the need of elevator down deflection, thereafter decrease the fuel consumption and increase the range.