Quite. Logic dictates that if, (given similar terrain) you are be able to move x number of large stones over x distance, you would be equally able to move a number of smaller stones over a longer distance. The time it takes and the manpower needed might vary but ancient builders weren't tied into construction contracts but (more likely) into seasonal dictates.

We'll probably crack the conundrum of 'how' and 'from where' eventually. Having lost the box with the instructions years ago however it's still fun to speculate - "Whichever way you turn are doors. Choose." :-)

A game of Henge, my masters?
The pieces are set. We lost the box
with instructions years ago.
Do you see Hangman? Or
Clock Patience? Building bricks
the gods grew out of? Dominoes?
It's your move. You're in the ring
of the hills, of the stones, of the walls
of your skull. You want to go?
You want out? Good - that's
the game. Whichever way you turn
are doors. Choose. Step through, so...
And whichever world you stumble into
will be different from all the others, only
what they might have been,
you'll never know.

Philip Goss