Incubator to Maran

[Aylesbury2013]

I have 6 duck eggs in my incubator and my maran i have has been sitting for 4 days now. I have set her before but she gets off at 18 days normaly ... should i just go for it and put my eggs under her ? The eggs have 5 days to go before hatching and this time i have put her in a box so it is nice and dark and cosy for her.