Hi. A friend of mine asked me to make two cakes for her with the use of marshmallow fondant, my question is, would the same amount of marshmallow fondant be used compared to readymade (rolled out) fondant? 

She is asking for 1 5" x 3" cake, and 2 7" x 3" cakes. According to CraftyBaking, a 6" cake would need 18oz (~510g) and an 8" cake would need 24oz (~680g) of fondant to cover the cake. Assuming I'll follow these measurements, would approx. a 1 1/2 batches of Marshmallow Fondant (http://www.craftsy.com/recipe/marshmallow-fondant) be enough? There are some other things to be used for the fondant, but for covering the cake, do you think it's enough?

The x1.5 of the recipe yields about 2,131g (75oz.) (Weight of ingredients)