Hi Jonathan,
The Kangaroo is not a delta, it's a swept flying wing. The reason that elevons are the best solution for this type is that the moment are is so short at the centre span, the sweep back increases the moment arm at the tips and gives better leverage for the elevator function. Unfortunately we also need the full span to give leverage for the aileron function, so the best compromise in elevons. I don't say splitting the functions would not work, but I found the elevator a bit numb on my Roo's and this would make it worse.
See Ya,

John