I've not yet written it up, but I'm going to CHIRP it, but not file an airprox. I'll include the tape transcript in my CHIRP report.
My reasons for the latter is that I discussed it with the other pilot, he didn't particularly accept that somebody was wrong, and it's unlikely that a call from the Airprox board will change that just create ill-feeling. CHIRP goes to a wider audience, is more thoroughly anonymous, and I hope that way some wisdom will get out there in a way that, I don't think an Airprox report would generate in this instance.
G