Nice word JTF, but I don't think it's in MWD10.
Sorry about that,
continue from
unratable
Tearable is a legitimate word in MWD10, but I don't see untearable.
As far as I can tell, UNRATABLE is the limit to this ADD-a-LETTER game.
We'll have to wait for Mac to move the game on.
There is at least one word that can follow SPLASHY.
Add an A
FLEA, LEAF, FEAL