Hi,
Here is my sentence, and I put hyphens where I thought they need to be; however, it looks awkward:
She has a 9.8-feet-per-second running-rate average.
No kidding, it certainly is awkward. It's better to avoid using a lot of these hyphenated kind of adjectives. Compare this version.
She runs at an average rate of 9.8 feet per second.
Best wishes, Clive