Should stay the same
 

your plane should balance out at the same location.

Center of Gravity
 

Something that you also want to check, is that when your airplane is level in comparison to the wings, not the gear, that your cg is still aft of the axels. If it isnt, it'll nose over on takeoff every time.

Center of Gravity
 

Oh yeah, and that affects where the main gear goes, not the CG.

Center of Gravity
 

That's it! try sticking your gear on with a bit of tape, or a drop of glue to check it before you put it in place permanently.

Center of Gravity
 

One thing not mentioned above; if you get the main gear too far forward of the CG, landing will become difficult. The plane will tend to bounce back into the air very easily. As a general rule, having the axels of the gear right under the leading edge of the wings when the airplane is level is about right.