Does PUN 1 change the data after it's been written to a view using IPunObservable?

What I'm looking for is a way to write data to a stream just before it gets sent over the network, the data can't be modified in any way after its been written. Does IPunObservable work for that? In other words, does PUN 1 not modify the data at all after it's been written using IPunObservable? If it does modify the data, is there anything else to use instead?

Also, is there a way to read and modify the data a photon view receives before it sends to wherever the data is supposed to go (RPC, Voice, etc.)?