In a story I'm working on, a nation of humans with WW1-level tech and some concerningly fascist leanings encounter a late-medieval society of dragon-like creatures on a distant continent. They are sentient and sapient, have opposable thumbs, have 6 limbs (4 legs, 2 wings), and are roughly 5 or 6 times as big as a human. Some of them can breathe fire, but other breath weapons such as incredibly toxic and acidic saliva or jets of supercold gas exist. For an idea of what they look like, here's an image:
The humans saw these huge, majestic creatures, and immediately came to the ridiculous conclusion that they'd make perfect slaves. Yes, enslaving sentient creatures who are five times as large as you, can fly, and can breathe fire is a completely and utterly insane plan at its absolute possible best, but try explaining that to the humans.
So naturally, the humans set about capturing and imprisoning dragons. The dragons they captured were chained up in overcrowded and cramped holds of their ships in preparation for the long voyage back to the Human continent. If you think this is sounding very similar to the Middle Passage in the African slave trade, you wouldn't be wrong. It is very similar in all the worst ways.
Thing is, these humans may be utterly insane, but they aren't stupid. They'd like to keep the dragons bound up in a fashion that lets them cram as many dragons into the hold as they can. This leads to my main question;
What position should these slavers bind their 6 limbed, winged captives up in to allow for maximum use of space?
Note that the position the humans bind their dragon captives up in has to be 'natural', in that the slavers don't have to dislocate any joints or break any bones to get them into it. This in no way means that the position has to be comfortable.
EDIT: Note also that the humans are really adamant about keeping the dragons below deck, partly to make escape harder and partially out of concern for maintaining the 'quality' of the 'cargo'; dragons below deck are somewhat protected from inclement weather encountered during the journey.