Well, I've just gotten Flite's unit selection up to roughly the same quality as Festival's, by filling in a few missing pieces in the join cost estimation and fixing the Viterbi decoder. The scoring, and the actual choice of units, is a bit different, but it sounds pretty good regardless.

It's a bit big though ... well, it's huge actually (so "small, fast" is not entirely accurate when it comes to unit selection voices :-) With 15,000 units and 150,000 frames of LPC plus residual data in a small unit selection database, one would expect it to be. This means that the really fun part of my task is just beginning.