Inside of this tour I will bet at least one bomber expert whill have determined the delay on salvo to lay strings of bombs down the main roads to take most of the buldings in 2 passes with a box of Lancs. Should just be a large figure 8 style traffic pattern.
A delay of 0.22 seconds seems good when using 500lb bombs. It leaves just a tiny bit of overlap to compensate for the slight randomization of hit locations. When using 250lb bombs, a delay of 0.17 seconds will give you more overlap, but still leaves you able to cover about the same area with the same tonnage of bombs. Results will vary at different altitudes, higher up creating a more dispersed pattern.
You can take out most of the buildings along the main road in one pass this way, with just a tiny bit of luck.