I advice: Don't let the camera determine the shape of your final composition in print. You decide the shape of your final composition in print.
Analogy: Just because a bucket has a round opening, this doesn't mean I can't put square, rectangular or triangular items into the bucket. It doesn't mean that I can't use the bucket to make a square sand castle. The shape of the bucket has no bearing on the final composition. Nor does the shape of the negative used to make a print.