Great thanks for that, though it seems yours is a later model so most of it is pretty different.
It does seem the sync generation circuit is mostly the same though, any chance you could take a picture of the underside of the main board?
I did make some changes last night as per other pictures I've found online (anyone know how to get hold of the owner of
http://ataricomputers.altervista.org ?)
All I seem to have achieved is a super wide image in 31khz mode. I'll keep plugging away, if I find the magic formula I'll report back.