Hi Doug
Placing the lintels onto the tenons is no big thing, I believe the BBC experiment did actually involve tenons, but they did cheat a bit by erecting the second upright with a crane, thus ensuring that the tenons were the right distance apart for the lintel. Keep your eyes open for the Stonehengineers coming to your TV screen soon. And if you're really interested read the Guardian for the next few weeks.

Hi Doug

I haven't had my nose in here for quite some time, so apologies for being late picking this up. I assume you are THE Doug Weller, ex-moderator of the Usenet group.

Anyway - tenons. It would be a simple matter to place a timber of equal or greater thickness than the height of the tenon on each side of it. The lintel could be raised by means of a ramp or crib and then be slid ontop of these. Levers could then be used to raise the lintel slightly while the timers are removed. So, I guess it's a case of "ET go home". :o)

Steve Gray