If you use the 12" boye cable, with the needle lengths (4" each) the smallest you can make is 20". Also, the cables are kind of stiff, so yes, if your pattern called for 16"s, that would most likely be a problem.
I was considering Boyes so what I did was buy a set of two needle tips and one cable from Hobby Lobby (they sell them separately, and they were on sale 50% off ) so I could try them out. I'm glad I did because I really didn't care for them due to the stiffness.
If your LYS carries both sets they might let you try them out.