Just thinking about what I posted above:
So if I keep the distance between the two Focal Reducers at around 175mm I should be ok (I hope)
I still don't think that's right.
It would be correct if the focal point was hitting the camera chip, but it isn't. It is hitting the 2nd Focal Reducer. By the time it passes through the 2nd one it will be out of focus by the time it gets to the camera chip
Am I way off here?