This is all getting a bit weird Jon.
I've just logged on to the Felder Owner Group forum, it's still up and running and it's still managed by Yahoo. However there seems to be a bit of a brouhaha going on, with one faction wanting to break away from the Yahoo structure (makes sense to me, it's really clunky) and start again elsewhere.
I get the impression David Best is involved in this debate somewhere, and possibly access to his manual is a casualty of it all? Just a guess, but I can't find any route through to buying his manual anywhere!
I've also checked the manual itself and there is no ISBN number. One other thing, David has started to write a companion manual covering Felder planers and he kindly sent me a draft copy, that's worth looking out for too.
I don't know if you have a new machine or a used machine, but other documents you might want to chase down are the original Felder instruction manuals, which are pretty hefty and give quite a lot of information,
Good luck!