Read this one about stepping, like I was mentioning but haven't found anything on crossing:
Some pilots preferred more than one point of convergence. In 1944 operating out of England, American Lieutenant Urban "Ben" Drew set the .50 in guns of his North American P-51 Mustang "Detroit Miss" to converge at three points: 600 ft (180 m), 750 ft (230 m) and 900 ft (270 m), with the inboard guns aimed closer and the outboard guns farther away. Drew felt that this gave him a suitable concentration of fire over a deeper envelope of engagement distance
Also found this:
A very close convergence point proved devastatingly effective for some pilots. The highest scoring fighter pilot in the world, German Major Erich Hartmann, set the wing guns (later cannon) of his Bf 109 to converge at 50 m (160 ft) because of his preference for waiting to attack until very near his opponent.
