steinsato - I recommend you also take a look at BM's Sterling Gold recipe, which is linked in his Recipe Drop-Down. It's a fantastic beer, he sent me a bottle once. Mmmmm.
Your best bet might be to combine the Sterling Gold recipe and this recipe, producing a modified version between the two beers.
In short, Sterling is a very "mild" and interesting hop to work with - while Citra is a very hi-power citrusy Pale Ale-type hop - but there's no reason they can't be combined to come up with a pretty delicious combination - it just won't be an exact replication of Cascade + Centennial.