My comments about the Greek word-medial consonant clusters -φθ- and -χθ- being pronounced [pθ] and [kθ] (<– IPA)  caused a bit of discussion (and many thanks for Suzanne’s related, neat link).

I know that some found my claims wanting, but in my studies of other Greek issues (particularly Greek voice & my continuing review of Paul Danove’s book), I have come across some more evidence where the orthographic γ becomes χ preceding the -θη- passive form. Here are a few examples:

προάγω

Esther 2:21 προήχθη

2 Maccabees 5:18 προαχθεὶς

3 Maccabees 3:16 προήχθημεν

Wisdom of Solomon 19:11 προαχθέντες

Now in light of these examples, we must ask: Is it possible that there is a phonological rule behind this orthographic change?

Yes. It is possible. But is it likely? Is it likely, particularly in light of the already know phonological rule for doubled consonants:

[W]hen the doubled consonant is φ, θ, or χ, the resulting form shows πφ, τθ, κχ–e.g. ἀπφῦς, τίτθη, κακχάζω. Such a spelling indicates that the lengthening of these consonants consisted in a stop* element (π, τ, κ), which would not be appropriate if the original sound were a fricative, but entirely so if it were a plosive: thus [ph, th, kh –>[pph, ttph, kkh].

Allen, Vox, 21.

If anything, the evidence I have supplied here should bolster the claim that the first consonant is a plain vanilla stop in χθ just like in τθ.

Personally, I doubt it. I’ll be sticking to my original claim.