if you get a ring sling, get an open-tailed one. They are fully adjustable - which is easier to use for safety and secuirty. The ones with padded rails are not fully adjustable and are really somewhat adjustable pouch slings. True pouch slings can be ok, if you get the correct size - this is very important. The vendor should be able to help you get the size right. With a little prem, I'd be very wary of the pouches, as it will be extra tricky to get safe positioning, I think.
oh 5kg! ok, she's not that small then

I agree abouty the breeze baby sling - can be diggy on the shoulder. although with a 5kg baby it's probably ok. is the rockin baby one a padding rail one?