The new version of Visions Of Chaos now supports Hybrid Mandelbulbs.
The basic idea is that you alternate the Mandelbulb formula between iterations for each pixel. So for example the 1st, 3rd, 5th, etc iterations use the regular positive SIN Mandelbulb formula and the 2nd, 4th, 6th, etc iterations use the Rucker variation.
Here is a quick sample movie.
More sample images can be seen in my Hybrid Mandelbulb Gallery.