Okey doke, then, for all ya'll background folks, turned up a diary by a young Lieutenant, Inui, Genjirou, who was there, that sheds a lot of light on wtfo with 28th IR, Ichiki, Kuma, Mizuno, etc..
Ok, 28 IR is on Guam, Ichiki gets orders and gallops off to Truk with II/28th and the regimental support companies. He gets there on 08/13 and right away splits the force, taking half of each inf coy, the Bn MMG coy, a couple Bn guns, and some engineers, on his hare-brained conquest of Guad from 1st MarDiv.
Thinking rationally, Ichiki would have been aware of the limited carying ability of the 6 DDs, so structured his conquistadores to fit and sprints to his goal, while the rest of his advance force (in Boston, Daifuku, and Idunno Maru) wallows in his wake. Inui doesn't say how he split up the company elements, and your guess is as good as mine.
What Inui does say is that he was part of the 2d echelon, that included;
The "rest" of "HQ" and the "rest" of no 1 - 4 inf coys; the AT gun coy, the 8th Indep AT gun coy, the rgt gun coy, and another constr eng coy.
And those vestiges became the Kuma Bn. The HQ and inf folks became No.1 and No.2 company; the weaps folks stayed the same; and everybody got sucked into Kawaguchi's 35th Brigade.
So what became of the I/28th and III/28th? Inui's diary references meeting an aquaintence from III/28th. Since the 28th IR support units were assigned to Kawaguchi, and he burned them unmercifully, there was nothing left on which to hang the poor dumb sumbitches of I/28 and III/28. Seems they all went into the pool to flesh out operational units and simply disapeared from our charts.
So what's the point of trying to squeeze Ichiki or his 2d echelon into the OOB? I mean, 400 infantrymen assaulting 1st MarDiv? Wtfo? Game doesn't, and can't, accommodate that degree of graininess, so what's the point, except to be 'oh, so historical'. So we got a little bit creative. Hope ya'll appreciate it.