Now, with the patch around the corner, we can put the matters of the first volume to rest and start planning the matters of next one.
It would probably be good to set a cut-off point for it in earlier stages of its development, to have a clear goal before us and whatnot.
So, the question is, where that end point of Volume II would be? I nominate the end of ch009, "Family Matters". It ends with Kyon joining the Tsuruya Family (and a little joke with his own family about it), and this scene I believe could serve as enough of emotional high-point to give the sense of completeness to the volume (despite main plot of the meta-arc being far from conclusion).
For comparison, next clear-cut meta-arc, "When Cicadas have a family vacation", begins at ch015, setting a nice and steady rate of four-five chapters per volume for a couple of future releases.