Here's another tripod extender.
I originally developed this to shoot bald-faced hornet nests. (The first generation was docile. The second blasted out of the nest, smacking into me in their zeal.)

Details in following photos.

The tripod is a Leitz, but any sturdy tripod should work. You want to position one leg as much under the camera as possible. You may also need to weight the back tripod legs or the back end of the tube.