The others have pointed out that in your example, you've greatly increased the fin area. However, that's not the whole story.

One very important change that's also happening is you're increasing the

aspect ratio of the fins. Aspect ratio is defined as b²/S, where b is the fin semi-span (the thing OR calls 'height') and S is the surface area of the fin. Higher aspect ratio fins are more aerodynamically efficient. For the same total surface area, at the same angle of attack, a higher aspect ratio fin will make more lift. This effect is independent of the effects others brought up such as the fin being "hidden" by the boundary layer. The lift curve slope as a function of aspect ratio can be found with the following equation:

View attachment 569413
where α is in radians.

If we graph this equation, we get the following:

View attachment 569415
Most rocket fins have aspect ratios around 1 or so, so as you can see the lift curve slope is

*very* sensitive to aspect ratio in that region of the graph. A higher lift curve slope means that the same deflection will lead to a greater lift force, thus pulling the CP backward.