Elger,
You may find valuable info here:
http://harringtonmuseum.org.uk/DZ%20...utumn%2007.pdf
An Halifax, which I believe from your website is an aircraft of your interest, could hold 15 C-type containers in its bomb bay.
This was the standard RAF type of container, six feet long.
A Whitley could carry 12 containers.
Groet,
Leendert