Hi, I've just been cleaning my Douglas MkV 1951. Between the frame and gearbox/engine there is what I think is an adjustable spacer, of which was loose. According to Spannerama these are found on Plus and Dragonfly models, which I assume is why I can't see them in my spares manual. When I extend the spacer should there be anything between the gearbox/engine spacer to protect the alloy? Is this spacer incorrect for this model? How tight against engine must it be? Thanks for any advice. Paul J