Can you post a picture of the plane? What is going to determine this is whether or not the quarter chord line of the wing is straight or swept. The CG is located relative to the Mean Aerodynamic Chord (MAC)
, which means that if you have a swept quarter chord line, then changing the span will affect the CG location. The greater the sweep, the greater the change in CG position, and vice versa.
On a rearward swept quarter chord, shortening the tips will move the CG forward from its original location. I suggest you re-calculate using a CG Calculator
based on your plane's current specs.