Your HQ dealer will have rulers that are designed for your S16.
A good dealer WILL let you try them before you buy.
When I test drove the machines last spring, I asked about the rulers, and out they came to try.
They are expensive, so I would buy one, and only one for a starter
... and see how I liked it before I bought several.
Actually, I might not buy any ... get accustomed to the machine and FMQ first before adding on the extra step. You can always buy them later, and as you see the need. Kind of like the assorted rulers many of us have for cutting ... we later wonder why we have so many!!
From what I remember, there is one that is a multi-tasker
... which gives you a straight edge as well as some curves.
That'd be more likely what I would buy ... more value for the money!