The three holes F,G and H are unacknowledged and unknown to most people.
But they are evenly spaced and useful in constructing alignments.
See http://www.sarsen.org/2012/07/stonehenge-resurrection-alignment.html - Station Stone 94 to G and Station Stone 93 to H are parallel and point to the midwinter sunrise.
Cleal provides the information but as to whether they were stoneholes, postholes or bush holes I will leave to you to judge. They are circled in the plan below.