I have tried all methods of changing the skybox,you
can change it using a trigger zone,never encountered the problem of only part of it changing I found that the whole skybox changed no problem.The problem however is that the sky box will not change to anything else after doing this once, it just seems to get stuck,which caused me all sort of headaches if used in a test level,anyone trying to use this method should never try in test,you will only screw up FPSC, only try it in a built game you will see what I mean.
I have no idea as to how you would change the .fpm if you could elaborate I would be much appreciative.
Until TGC implement this function into FPSC there appears no way to do this,anyone who knows a way can feel free to contradict this.But only if they provide the answer and some evidence of having
actually done it