No, I wasn't kidding. You are right to site the rules for verbal forms; and
I would simply add that the one over-riding rule in Koine greek is that
writers often break the rules!
The authors of NT texts were no more bound (and most less!!) to strict
grammatical constructions than are modern authors or poets.
Jim
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Jim West
Adjunct Professor of Bible,
Quartz Hill School of Theology
jwest@highland.net