I usually setup my chronograph about 4 inches above the sensors, about 3 or 4 inches away, and on a table to make sure both gun and chronograph are leveled with each other. This setup guarantees I dont shoot my chronograph.
I set up mine at a minimum of 15 inches away from the muzzle and maximum of 36 inches. Above the sensors is about 4 to 6 inches. I always use a flat table and try to keep the gun in the same position for each shot.