Dave de Vos
I read your description of type "C" and type "D". I think your description of "C" would be closer to IP / IS and "D" to Aiki. C would then be a prerequisite for D.
I would personally define internal as it relates to what I learned from/of Chinese internal as:
The Ideally most efficient use of the body as a tool. Relating especially to physical structure and alignment.
say this is something relating to "C" or something similar or something different all together? How and/or why?
I can see how "C" might be an important part of learning "D" but not a necessity. Could you briefly explain a bit more?