I went back today and did some digging, it turns out you are correct in saying that core 4 works, because I removed the core 6 from oodle rec and replaced with core + ext 4 from poodle and I got better results than poodle:
Here they are side by side. "kraken" is oo2reck while poodle is poodle.
Tested on Data4.bdt (516mb).
Update: Precompression has worked, here is result:
