To all, My mail has been bouncing, and I don't know if this made it to the list or not. If it has, I apologise for sending it twice. I have just been notified about the new site devoted to Archaeopteryx.
Symmetrical feathers are perfectly capable of generating as much lift as an asymmetrical feather.
The extra weight required in the shaft of the symmetrical feather isn't enough to affect the flight mechanics or power required to fly, but might well be enough to substantially impact the biological cost of the molt, which may have been related to the eventual development of the asymmetrical flight feather.