Well I googled that up Doug and there are some aviation enthusiasts discussing the subject here.
http://forum.keypublishing.com/showthread.php?56511-Drop-Tanks
There are reported incidents of them hitting the likes of what you say. If it hit a building it usually survived, not so for living things. They pale in to insignificance compared to some units that were fitted in to the bomb bays of Lancs(?) and so on. Don't know in what context these tanks were used. Huge great plywood things. There are the (very disintegrated) remains of a couple in different spots high up on the Peak District moors where they were jettisoned. Reckon you could have killed a flock of sheep with just one :-) Now they were big enough to make an 'extended family' size side car.