Thanks for the comments and suggestions.
The domino idea sounds fun, there is probably some mileage in that
but it looks like the primitive humans are the way to go. I had more or less decided this myself but was hoping someone would have a cool idea that avoided my having to make them.
I got the impression from the book and I read that before seeing the film, that the monolith was able to change its scale and appear any size as required. My object is about the size of T.M.A.-1 as it appears on the moon in the film. Although it is described as perfectly black in the book I gave it a slight secular sheen as seen in the film.
I am a little surprised that it hasn't appeared in the TG2 universe before. Although that 0.9 appearance looks good.