I'm finally back on this part of the build. In re-reading the thread, I followed
xpflyr's pointer to this thread:
http://www.wingsforum.com/viewtopic.php?f=218&t=18900. It contains a page from the "old" manual that showed a different attachment of the flap return spring. Mounted at the wing root, the spring runs between a tab on the flap spar and a tab under the head of the rear wing spar attach bolt.

- Flap Return System - Just Manual Fig_6_13_2a.jpg (56.07 KiB) Viewed 4193 times

- Flap Return System - Just Manual Fig_6_13_2b.jpg (19.15 KiB) Viewed 4193 times
I see some advantages to this system:
Eliminates holes in the leading edges of the flaps and the trailing edges of the wings.
I'm wondering why this system was abandoned in favor of the more complex one used today. One guess would be to eliminate asymmetrical forces on the flaps. Anyone know about this?
To mitigate the possibility of spring stretching from gusts catching the flaps, I'm looking at putting a small bumper protruding from the hinge plates at the flap control arm, limiting the arm to 45 or 50 degrees of travel. I think an adjustable end would be wise, perhaps with some resilience. Any suggestions or comments?