Flash extenders

I am going to Namibia in late April, before a longer sojourn to the Dark (or Brighter in my opinion) Continent in the fall.

One thing I have yet to properly try in the bush is a flash multiplier (not sure if that is the correct term) in order to add a bit of fill-in flash to some shots. One I've heard of is The "Better Beamer"
Walt Anderson Flash Extender at www.birdsasart.com

Does anyone have any recommendations or experience with flash multipliers?

I would likely be using it with a Speedlite 580EX on a 1Ds Mk II with a 600 f4 and Wimberley gimbal head.

To be honest I'm still unsure whether I want to use flash in this way as I am uncomfortable with the addiitonal intrusion factor for the wildlife. ALso the flash may casue them to react and move off far more quickly than I would like.

Any comments would be appreciated.

I have used the Better Beamer and it does a very good job of extending the range of the flash. How they affect wildlife and birds seem to depend on the animal. Some are skittish and will react to the flash while others are oblivious to the fact that the flash even went off. And then there are those that do notice the flash, will curiously look in the direction where the flash came from and then carry on with what it was doing.

The bigger problem, I think, with using the BB is the fact that it can act as a huge magnifying glass and burn (melt) a hole in anything that's black and made of plastic, like the flash itself or the lens hood. I think it can even etch a mark on a metal lens barrel. When using the BB, you really have to be mindful of where the sun is relative to the BB lens.

Leo, gives good advice...

Here is a write up which gives some visuals on what it can do.

http://www.naturephoto​graphers.net/tdg0502-1.html

Excellent. Thanks for the help Leo and thanks John for the link