The Polesti raid was not the only place heavies were used at low level.
I've seen quite a bit of footage where formations of bombers fly over areas at very low levels carpet bombing enemy positions to clear troops and tanks, sometimes they very low indeed.
As to releasing the bombs from the pilots' position I tender this sentence from a thread Karaya posted elsewhere.
Graham immediately salvoed the bombs from the pilot's pedestal while Kamenitsa fought to keep the plane under control.
This was in reference to a B24 that was in trouble and was going down. Judging from some of the footage I've seen of the low level bombing runs in late war Europe the bombsight would have been pretty useless at those altitudes, so I'm hazarding a guess that the bombing here was also "guestimated" from the pilots' position as well.
