I started running my Brit with an astro when she was about that size. I'll admit, it looked a little obnoxious, but she got used to it pretty quickly. I wouldn't say it slowed her down in the least.
I hunt two dogs of my own, and sometimes hunt with others and their dogs. A little dog is so easy to misplace, especially a pointy dog, when there are multiple dogs zipping around in good cover.
To me, it's worth the price, but everybody has their own opinion. Good luck with your little dog. If I had to get another dog, a FB would be near the top of the list. :thumbsup: