Help with difficult positioning -

I've attached a mock up of the page I'm trying to make. I currently have everything working properly except for a big arrow image that overlays multiple divs. I'm trying to find the best way to put it where it goes, but honestly don't know where to start.
I've attached an image of what it is supposed to look like and below is a link of what it looks like now. Right now I just have it absolutely positioned, but obviously that doesn't work with any variation in window size.

any tips would be much appreciated! Thanks!

What it looks like: bradnelsoninc dot com /test/layout.html
What it's supposed to look like: /test/mockup.png