Yeah...strings can be difficult. One trick I have learned is to divide the parts of a string section and to record them separately. Then when mixing I create a stereo mix, panned to about 60-70% left or right or so till it gives a nice visual image if you close your eyes and listen. Cello's a little to the right, viola's more centered. I hope David K responds as he has done some awesome string mixes. Separating the parts gives some "air" to the sound. Another thing...don't let 'em get in your face too much. Depending on what else is happening, just barely there seems to work best for me, giving the suggestion of distance and depth to the sound stage
chazba