Steves anchor stone would probably work more efficiently if it was half buried as well as staked.
On the other hand that would bring us into an interesting and perhaps dangerous dialogue with the archaeologists as to where was the archaeological evidence. It would be tempting for us to point at the Aubrey holes, but it would be a high risk claim. On the other hand, they are placed precisely opposite each part of the outer sarsen circle in the way you'd expect, and original use for construction purposes isn't precluded by the fact they had significant astronomical placement or subsequent ritual use.

It's a ticklish one. Should we stick to just stakes, on the grounds the evidence for those won't be there, even though we may secretly think putting the anchor in a hole might be more efficient and more likely?