Depends on how big your tank is and what type of flying you do. In the "Patty" a 24 oz tank will move the CG back as much as 1/2" during a flight. A 16 oz, maybe 5/16".

If you fly precision maneuvers, IMAC or 3D, that much will throw you off, but if you just fly for sport, you might not notice it.

Let's put it this way: It's a lot more noticeable that switching to digital servos, but not as noticeable as adding expo.

Jim