RJS,
In my own case, old ideas that I have seen proven many times die very hard with me. Perhaps I am totally wrong in what I believe, but I know it is possible to modify the quality of the light being projected (Penumbra) through an enlarging lens. I am not saying you and Ctein are wrong, but simply I disagree with the theory that another element introduced in the Penumbra has little or no effect on the final image. I admit I have never read Ctein's book, and most likely won't so I will take my silly notions with me to my grave.
Thank you for giving me something else to consider and I assure you I will consider your information. Right now I am trying to recover from my dumb mistake of believing I needed MC filters when I already own a late model color head enlarger.

Again I thank everyone for their interest and sharing their information with me!
Charlie............................