YP, many thanks for your response.
Apologies for any vagueness in my post, but my main interest here is climb derate.
Aircraft Performance is a major part of my work, but climb derate usage policy seems to vary significantly depending on who you talk to. My understanding is that climb derate is more of an operational decision as opposed to take-off derate which clearly has major safety implications.
PS - Before someone else chips in - I believe that the screen heights for dry & wet runways are 35ft and 15ft respectively.
Again thanks of taking the time to respond.