Sounds like you want to experiment with the Pan Law in Logic to -3dB.
Here is the Pan Law settings explanations from the Logic 9 manual (p.1228):
"Pan Law pop-up menu: Signal spanned to the center position may sound louder than signal spanned hard left or right. The Pan Law value determines the amount of volume reduction on signals that are panned to the center position. You can choose from the following settings:
0 dB: With no change to the volume level, signals will seem louder when panned to the center position, in comparison with extreme left or right pan positions.
-3 dB: A full scale signal (0 dBfs) will have a level of a -3 dB when panned to the center
3 dB compensated: A full scale signal (0 dBfs) will have a level of 0 dB when panned
to the center position (or +3 dB when panned to extreme left or right positions). "[/i]