Stopping fixed position at a specific div

Hi, thank you for this elegant plugin!

I am hoping you can help provide a solution for having the menu stop scrolling when the user scrolls past a certain point, namely entering a new div that I can give a class or id like #fixedStop

I imagine this feature would be very useful for footers, etc. for others who use this plugin.

Thanks for all of your work!

The page I need help with: [log in to see the link]