For AB spacing of small chamber groups, you should really be looking at 40-60cm between mics. 4-5 ft is wide even for orchestra. I usually max out at 3ft. The idea is to have good frequency separation without creating a hole in the middle. The 40-60cm number is kind of the magic distance that DPA suggests. If you insist on going wider, then you really should look into a center mic. Or if you need more obvious channel separation, go for a coincident pair or directional mics.