I was in the studio when he was working on the Kronos Quartet piece. He played some of it for me on the Synclavier. The patches or samples he had set up were of string sections - big and lush. That's how he was already hearing and conceiving the piece (orchestral, as usual). I remember thinking (to myself) "Frank, what the hell are you thinking? There's only four of them. It won't sound anything like that". David Harrington told me once that Frank wanted them to record the finished piece and put it on an album along with the Synclavier version. Of course, they didn't.
This also reminds me of what David told me he said about the Ear Unit line-up when he was working on "While You Were Art" - something like "What an unfortunate instrumentation". (David has no recall of this!) Interesting, since so many people in the new music community seem convinced that the Pierrot + percussion group is almost the ideal vehicle for great ideas in chamber music, and that the only way it could possibly be better is to have a soprano as well!
I also remember the exact words Frank used once, although I don't recall just what project we were discussing (and truthfully, I don't think it was the Kronos piece - more likely the lack of resources he suffered on the Orchestral Favorites album). He said "You can't do anything with a string quartet". Obviously a few other composers would disagree.