Saito 100's run very nicely on a 14x8 or 15x6 with RPM's somewhere around 9500 (assuming at least 15% fuel). A 16x6 has a bunch more load than these and will probably drag the engine down into the 8000's. Not good for a Mustang that will probably want some speed to fly nicely. In fact it could make the maiden very interesting.

I recommend that you spend the $15 and get a 14x8 or 15x6, at least to start off with. Its a whole lot cheaper than replacing the whole airplane.

Also if the engine is new then read up on how to break it in. The 100 is a real shaker the first tank or two, and most need a half dozen tanks or so and a good bit of adjusting on the low end before being ready to fly.