Tore Årthun, over from Norway on a bouldering tour for a couple months, asked me if a sit start to Grindrite at the Happy Boulders had been done (v3, page 125 in the new guide). I wasn't sure, as I had seen chalk on those holds below the regular (high) start for a while, but hadn't done a sit myself or known anyone to do it.
Anyway, Tore went back to complete the line: "The way I climbed it was from a sit start at the big undercling under the roof," he says, "slapping up right to a nice sloper, then moving left hand into a big undercling and slapping with the right to join the stand start." He suggested the difficulty was probably somewhere in the v8 to v10 range, though was more likely at the upper end of that.
Not sure if this is an FA, but it's not in the guide, and certainly should be now! Tore has suggested, Slave to the Grind as a suitable name, unless it was previously climbed. I'll go with that unless someone tells me otherwise. Thanks for the info Tore.