Maurizio,
Hey everyone- Usually I sit back and read and learn, however, I had to answer Maurizio's question on this because I have a good bit of experience shooting higher frame rates.
Maurizio- Make sure you really run some good tests in the 2K flow for your overcranking. I have been doing a good bit of that myself, and to be honest, I have not been very happy with the 2K results. If you were to tell me that you had to do everything at 100/120 fps, then you would have no choice. However, in your case you said you would be backing off of such a high frame rate for the most part.
If that is the case, SHOOT 3K!!! I started doing that, and the results are far sharper and far better then going with 2K.
If you are using a hard-drive with the camera, and you are have "redcode 28" selected in quality, you will be able to shoot at 3k 2.1 at a max of 60 fps. It makes a major difference.
In my opinion, try to avoid the 2K at all costs unless you have to use it for something above 60fps.
2K is pretty soft, even with the best lenses.
I know you mentioned about blending the RED footage with the 16mm- I am not sure about everyone else, but I would get all the resolution you can while on location and then deal with blending and matching in post.
Good luck on your shoot!