How to customize Finder's Share menu? Is there a way to add custom services to Finder's Share menu?

I have created an automator service to copy selected files to my Dropbox directory (similar to this).

I enabled this service in the keyboard preferences.

Now I want to add this service in the Share menu rather than having it in the general contextual menu.
I haven't tried it but I would suggestion following : 


Copy your automator service in /System/Library/PrivateFrameworks/ShareKit.framework/Versions/A/PlugIns/
rename it Servicename.sharingservice
Now edit /System/Library/PrivateFrameworks/ShareKit.framework/Versions/A/Resources/SHKServicesOrder.plist by adding your service. (CFBundleIdentifier in Info.plist + function name)