td, I think the graphic will explain, the SC 250 bomb had mounting lugs on the nose for vertical carriage, also on the casing for horizontal. Germans wanted all their aircraft to be dive bomber capable, guess horizontal mounting would be used in that event with reduced capacity in the bomb bay, but extended by under wing carriage.


https://cimg4.ibsrv.net/gimg/pprune....9c3c9dad8e.jpg

As for accuracy even the famed Norden bomb sight had issues, so I think going out tail first would have little detrimental effect.https://warfarehistorynetwork.com/20...beyond-belief/

I alluded to this in an earlier post,there were not that many Norden Bomb Sights available anyway - they were expensive and difficult to manufacture,so Formation Leads/Deputy Leads had Norden Sights and the other Aircraft 'Toggled' their bombs when the Lead Bombardier 'Dropped'.So therefore the Bombing Accuracy would be (at best) the same as the size of the Squadron Formations and of course relying on the navigation/accuracy of the Lead Crews.

An experienced ppruner once explained to me the inherent problem with accuracy for dumb bombs. The flight of a bomb relative to the ground is strongly affected by wind. Most sights had provision for adjusting for wind at the aircraft's altitude, but wind strength and direction normally vary with height; precise wind speeds could not have been known, and it's doubtful if a sight could have been devised that would compensate for them. So however exquisite the optics and ingenious the computation of a bombsight, it was always hit and miss, and mostly miss; hence dive bombing, and the first guided weapons, especially for naval targets.

And I doubt if the lyricist considered that. I was only reporting what I recall from my youth.

Forty Flying Fortresses ...
 

Yup, me too. Although the variant that my father recounted had 'forty Flying Fortresses' etc. 'and they all had a teeny weeny bomb.' Clearly British aircrew were fully aware that British heavy bomber design was based on the maximum achievable bombload, everything else was extraneous (a second pilot and decent defensive firepower spring to mind.)
Point above noted that the B-17 may have been derived from an airliner, whereas the Lancaster and Halifax were bomb trucks, pure and simple.

The aircraft was not derived from an airliner in the manner I think the quote is intended. it merely incorporated the construction techniques Boeing had developed in previous aircraft, the 247 and XB-15. The Boeing techniques were developed following inspection of a Tupolev TB-1, which they worked on when it passed through Seattle in 1929 on a flight to New York.

The Boeing 307 Stratoliner was derived from the B-17. The 307 was pressurised and as such, the fuselage section was completely different.