Max observed % FT improvement

A question to the Trainers here: What's the best % improvement you have seen in a relatively untrained athlete? I ask becuase I've managed a 34% improvement to date (training and getting quick wins with cadence etc) but still need another 30% FT improvement or so to reach the w/kg target I have in my mind.

I guess somewhere a genetic potential from untrained to max has to kick in?