Was thinking of getting a horizontal adapter for my tripod. Was wondering if it is worth the money or is it a waste because the camera weight would make the setup unstable?
http://www.feisol.net/images/PB-70_horizontal_adapter_kit_lg.png

Look again at the picture. Do you see the hook on the end opposite the camera mount? That is for hanging a counter weight such as your camera bag or something similar to stabilize the rig.

That looks very limiting. You would be far better of with a tilting arm, such as:

http://www.amazon.com/Promaster-Tripod-Accessory-Tilt-Arm/dp/B004ROO5QA

Harold

It depends on how much stability is needed, which in turn depends heavily on the lighting used, IMO. If you're planning to do natural light, especially at high magnifications and numerically large f-stops, you might consider if you anticipated exposure time will be short enough to minimize motion blur in a cantilevered tripod rig like the one shown in your link.

Also consider the total weight of the rig that will be attached to your cantilevered tripod extension. The heavier the rig, the more stressful it will be for the tripod to hold it steady. I continue to be rudely surprised at how much my total rig weighs (Canon 5DII camera body, MPE-65 lens, MT-24 flash). While extra weight can sometimes stabilize handheld work, with a tripod assembly I would worry about instability near the weight limit of the tripod and extensions. Recently I switched to a geared tripod head, and this adds additional weight and height to the overall system that is attached to the tripod.

As other have pointed out, adding weight to the tripod's hook is often very helpful to minimize vibration and to increase stability.

Thanks for the help full comments