Can anyone recommend a good double carrier/sling?
Not too bothered about the cost (anything which helps make the babies more manageable is worth it). Back support is the priority - I am already feeling about 82 years old! 
( I've found this thread, but it's quite old: www.mumsnet.com/Talk/multiple_births/1399153-Carrying-two-any-sling-wrap-recommendations-or-dont-buys )