Nice scope Murray.
TBH I don't think you'll ever have any issues finding a guide star at ~700mm FL with an OAG. Even if you have to slightly offset your fov it will have a very minimal impact on your framing. That and the fact your refactor is 4 elements which I suspect is a very flat unvignetted field. If the OAG doesn't rotate it's actually better for guiding as it stays square to the RA/DEC directions for mount corrections.