Clint
I think the "skull splitter" was there to ensure a quick death, instead of living a day or two in agony. You know, a preferable quick death instead of a slow one....
Anyway since it seems the Japanese chose the Dagnall Dagling as their preferred model (made a quick check and no sign of Slingsby or SG 38 anywhere) I would go for that one or one of the copies they made such as the Kirigamine models.
But then again, I also think these primary gliders all look more or less the same plus the fact that almost every "garage builder" probably thought he could change a bit here and there to claim his name to such an immortal design.
In my youth I spent one week in a glider camp with quite a few enthusiast trying to learn the ropes. I spent one week in the back seat of a Bergfalke and came out (luckily alive) saying never ever more without an engine!!
I kept that promise....
Cheers
Stig