Going to be running a 91 Saito and the rec range for props goes up to 14x8

Its going to be on a Pup and a few people have told me i should go high dia low pitch
My question is

Can you exceed the rec. range by lowering the pitch.

Would the 91 run say a 15 or even a 16 by lowering down to maybe a 5 or 6 pitch?

Or would it be inefficient to run it in such a way.

Thanks