I've been doing all of my mixing in Digital Performer and I'm not sure at this time of a Logic equivalent of this procedure...
DP has a plugin called Trim which can take all of the L/R data of the stereo image and narrow it down to mono, if you wanted it to. I narrow the string fields down to about 30 degrees in cases where I want the strings evenly spaced. Then, I use the pan settings to place the strings across the "stage"-- 5 sections x 30 degrees = 150 degrees with some extra allowance for the contrabasses.
Other times I fudge on this when I don't want the contrabasses panned so far to the right. Trimming to 45 degrees gives some overlap within the string section where this is desired. The problem I've been having with simple panning has been stated-- losing important L or R sonic data and to some degree, various samples "bouncing around" the mix a little too much where different samples of the same section are not totally identical interms of 180 stereo signal distribution. Not that it's uneven "per se"-- it's actually quite natural sounding on its own for the way certain instrument pitches and resonances come across, but too much violin 1 activity on the right side of the stereo field has been an issue. Altiverb 5 does well with how sounds coming from the left side of the mix interact on the right side of the room.
On projects involving other instruments (such as drums, electric bass, guitar, vocals, piano or electric piano) it's even more important that the stereo field be controlled. Such mixes tend to be cluttered with that "wall of sound" approach. Heavier compression in mastering (ick) further squashes the sound and squeezes the air out of the tracks. Narrowing the stereo field helps focus the sound better and keeps such mixes as tidy as possible. In these cases, the orchestra is often trim-narrowed and then panned within a centered 90 degree spectrum. This leaves the remaining 45 degree extremes L/R for any fancy "wide" panning of dual acoustic guitars or electric pianos, background vocals, or any tap delays (for pop and R&B mixes).
Generally speaking, trimming the pan field really does help (aurally) clarify the seating positions of the different orchestral sections.
As always, there is more than one way to do anything-- and what is *too much* is always relative and a danger.