Are the bikes competing for space with other stuff and have to be more compact? And are they brand new merchandise that has to look pristine until sold?
If "no" to both of the above, then I might just pile them in any which way you can and put a old towel, drop cloth or the tons of bubble wrap that you might be hoarding from packages received, between those that seem to be rubbing where you wouldn't want rub marks.
Of course be careful about the derailleurs. Consider whether the bikes will shift in a turn or from bumps and then they bend one or more DR hangers.