Occlusion Culling implementation problems

We have a fairly poor performance level that it'd be fantastic to get occlusion culling working for to get things moving faster, but I can't seem to get it working at all. I've used these tutorials in order to familiarize myself with Culling (If there's a good tutorial I missed, please let me know.):

http://unity3d.com/support/documentation/Manual/Occlusion%20Culling.html http://blogs.unity3d.com/2010/09/22/unity-3-feature-video-occlusion-culling-with-umbra/ http://unity3d.com/support/resources/tutorials/video-occlusion-culling

I've tried numerous ways to get the culling working, (using a view area on the entire level, using a view area on just the area we expect players to be in, using low, medium, and high quality settings, as well as larger and smaller cell sizes, and variations therebetween) but no matter what, the occlusion culling visualization in scene only shows Frustrum culling with no occlusion culling.

I've heard that the culling visualization for unity may be glitched and not properly show occlusion culling but can't find any evidence of this.

We're also using multiple child meshes in a single DAE parent for our environment, is it possible that this would cause issues with the culling? The Child meshes inside these DAEs are split into many smaller parts, and seem to work fine with frustrum culling.

Any suggestions on something that may be going wrong along the line?