because of the included angle of blumlein, it is more appropriate for farther distances(with bigger groups). Otherwise you risk not getting them all in the picture.
If any sources are 45 degrees or farther from the center line, there will be phase conflicts between the channels (because they'll also be picked up by the rear lobe of the other channel, in reverse polarity), and that will destroy your imaging.
Your Blumlein pair should be placed away far enough that it can "see" sources as filling 90 degrees or less.
for best playback results, your speakers should be at 90 degrees too.
I love blumlein so far. More than any other config ive done.