I decided to concentrate on suffixes. OID, AGE, ATE, ITE... Some may be quite low probability but it feels like tying up loose ends (excuse the pun).
I have also, as a separate exercise, spent some time on a very weak area - 6 letter blockers. This area still needs a lot more work but I have now created my own subset of 'non-obvious' blockers so it looks a lot more manageable.