I apologise but I don't get what you are saying.
The spreadsheet meant nothing to me. All it did was confuse and frustrate me. Sorry.
I really appreciate the help you are giving but I can't wrap my head around anything mathematical.
I can't do maths.
In your post you say
"Using the 140mm fl. So if that if it were placed 56mm inside the "new" focus for a further reduction of x0.7 the back focus would be 40mm.
This means that the distance between the reducers would be (175-56 = 119mm) and the final focus would be 40mm behind the second recucer."
Are you saying the distance between the 2 FR's should be 56mm or 119mm?
I'm lost
