You cannot take how a 39mm Calatrava wears on your wrist and extrapolate how it would wear if it were 45mm to determine how the Cubitus will wear. The best point of comparison for wearability is probably the Apple Watch which are 46mm or 42mm in length compared to the 45mm lug-to-lug of the Cubitus (ignoring the middle link, but the Apple Watch measurements aren't including the bands so I think it is a comparable measure).