Making Sunbeams through clouds

This might be a simple problem but I haven’t been able to figure out a solution yet.
I’m working on a “360 panoramic” environment to use as a skydome in the game engine.
Everything else is going well, but I want to put a sunbeam or two shining through the clouds (as shown below). The problem is, if I use a spot lamp with a halo, you can see through the clouds where the spot lamp starts and that destroys the illusion that it’s sunlight (instead it just looks like search lights shinning down).

Any suggestions would be very welcome. In the meantime I’ll keep working on it.

These kinds of sunbeams are sometimes faked with flat planes and transparent/translucent textures, even animated. Easy to keep the edges parallel, then, and they can be as long as needed to fade into the clouds above, or gradually fade out in alpha.

Thanks for the Help!
I can use animated “sunbeams” for other scenes. Probably will use them in the foreground to highlight important points.
I actually found another solution to the problem. I changed the transparency settings on my clouds texture to “Mask”.
This made anything and everything behind the clouds disappear.

They need not be only planes, either. Some games I’ve seen use cylindrical meshes for these faked beams.

Best way to think of tricks like that is … “I don’t actually have to fake a sunbeam. I merely need to fake what a sunbeam sort-of looks like in (specifically…) this particular situation.” So… y’know… what does “a sunbeam” actually do here? Well, maybe it glows a little. Maybe it de-saturates and generally fades whatever’s behind it. And so on.

(“How is Suzanne, behind a sunbeam, different from Suzanne, not behind a sunbeam?” How are the pixels different in one situation vs. the other?)

You could make a really long list here but you don’t need to… just pick a couple of easy-to-do key characteristics that will tell the user’s eye … “kewel! it’s a sunbeam!” … and none that will instead slam him in the face with … “OMG, this is fake!” Trigger the viewer’s visual memory with a few key characteristics, well-executed, and all the rest of them will just go right along for the ride.