I was asked about erecting some Avebury stones a few months back, I actually have some experience in such matters, shifting Avebury size stones will not be easy or quick, it was several weeks after it was first mentioned that I even worked out a possible way to move the 120ton one, then I heard that one is now on ice, the plan in our group is to try my idea on a 'little' 20 tonner sometime.
I was involved in the Brithdir Mawr circle erection, biggest stone moved was about 7 ton, that needed a minimum of 6 polepeople to lift wthout excessive straining using a simple pole lever, plus 2 giving instructions and packing, the pole we used was about 6" diameter hemlock and 23' long, shortened to 21' after getting a bit too ambitious with the leverage we could use when we had about 10 people to hand... That method doesn't scale well to 120ton stones, the pole levers would be ridiculous in size and need a small army. Our group doesn't use windlasses as they're too dangerous when they get out of control...
The group I worked with was an offshoot of Ivans, a bit more safety conscious. You don't move things that big just with levers and brawn, you need to think really really carefully about it.
I heard Ivan's group tried to erect a 20 ton stone and failed, I believe the stones they did move succesfully were similar weight as the biggest at Brithdir. I don't know of any other groups who've moved multi ton stones recently without machinery.
I've got lots of slides of the Brithdir work and really ought to scan them in and stick them up somewhere.
No idea if my group is one of the 'specialist contractors' or if we'll just be sharing knowledge, an informal visit to Avebury is slated for august.
