What about silver?
This has to be one of my fastest follow ups. After a few Facebook comments, I decided to try a similar test with a silver 7' parabolic. Here is a link to the initial blog post.
Again, I used a speed light at 105mm, 24mm, and with the built-in diffuser. As the silver is somewhat "focusable," I also tried with the flash at two different distances down the umbrella shaft from the umbrella, 32" and 21". Then I followed up with the bare bulb Speedotron head at three distances, 32" 22" and 14". I didn't bother trying the 7" reflector, as I don't think I would use that in a parabolic. Here is what the light patterns looked like.
The next test would be with a shoot-through, but I don't have a shoot-through umbrella. So I'll leave that one up to someone else.
Again, I encourage you to go and test your own equipment to make sure it is doing what you think it is doing.