Booklet with deffirent cover size

[PoleGhoulem]

salam

hello everyone i have this problem we have cover page with dimention litle bit deffirent from A3 (430x300)

our objectif is to print booklet with : A3 inside but cover with different size 

but as you can see in the screenshot the cover size option is gray and it's always as the paper of body (inside)

[Joe Arseneau]

You cannot do that, the cover and the body need to be exactly the same size paper as it (the finisher) can't possibly center the 2 different sizes. They just are not designed for it so the feature cannot be made available.