***** NOT A TEACHER *****
I have found something that may interest you since you do NOT want to change that main clause to the active voice.
Dangling: "To get the most out of a sport, the equipment must be in perfect condition."
The book says that we can change this to: "For someone to get the most out of a sport, the equipment must be in perfect condition."
So I was just wondering whether we could say something like:
"For Tony to improve his results, the experiment was done again (by him)."
Source: Wilma and David Ebbitt, Perrin's Index to English (copyright 1939 to 1977).
Student or Learner