The problem with "RINO" is that it seems to have no meaning beyond "doesn't agree with me about X."
Nobody seems to be able to provide a working definition of a "True Republican," and indeed that's a general and significant problem -- one of the reasons why R's in general, and conservatives in particular, have gotten into such deep political trouble over the past 25 years or so.
Conservative principles are quite straight-forward. Most people know them.