First off, I don't have V3, so can't give you any Figure specific advice on her. If I knew what you were trying to achive I might be able to offer more advice.

If your pz2 is overwriting data in a channel that you don't want it to affect, you can just delete that channel from the pz2. How are you creating the pz2 file? If you put a new valueParm channel in the cr2 named "valueParm xxx" then of course the corisponding part of your pz2 must refer to "valueParm xxx".

If you need to add a new valueParm channel to V3 in a way that you can distribute, you could try the method described in the link from post #2. Essentialy you create a cr2 that only contains your new channel, then use a readScript statement to Load the V3 cr2 into your cr2. I have found this seems to load rather slow, but it does seem to work.

I would not have thought any of this necessary, my understanding is that V3 comes with spaire channels designed for third party use, I assume this includes valueParm channels. If so then you should not need to create a new valueParm channel, you could just inject any paramiters into one of the existing ones. I think the third party channels might be the ones ending with "CC", but as I don't have v3, I'm not sure. Perhaps someone else could chip in here?