@regal1: there are a few more old RYA videos posted on the "GenesisArchive" utube channel. Most seem to be targeted toward beginner to intermediate and transition to the shorter 'fun' boards of the day. But some do have parts covering raceboards.
I liked how this video linked all the key parts of racing as well as the basics of light and strong wind board trim into one video, covering some of the 'black arts' as you mentioned. There has been a renewed interest in raceboarding around here so thought it was worth sharing this.