Earlier today I responded to a post about the KD tool, it read:
"My winter project was an m116 in an 82 380SL. I found that the KD tool worked great for compressing the springs to remove the rockers. When I decided to replace the valve stem seals I think a tool more of the design of the Mercedes tool would have worked better. You have to compress the springs much more to remove the cone halves and retainer. With the piston at top dead center using compressed air to keep the valves closed the KD tool had a tendency to push the valve spring retainer off center making it difficult to replace the cone halves after the new seals were installed. I think the original tool would have pushed the retainer straight down. It was not a big deal since I had the engine out of the car and on a stand, but if I would have been working with the engine in the car it would have been troublesome."
The tool is adjustable to achieve the best positioning of its components. With the cam lobe in the up position you just need to compress the spring enough to remove the rocker. As you compress the spring you will feel more clearance between the lobe and the rocker. You probably just need to compress the spring more than you are to achieve the room necessary to remove the rocker. Good luck.