Don,
please have a look at the german / french "retroplane.net" forum.
In this forum there are many Koverall experts also Walter and Stephan.
This guys builds only retro sailplanes of 1920 to 1945 with many tricks.
Thread Walter:
http://www.retroplane.net/forum/viewtopic.php?p=46740
Push at the link on Walter's Thread,
than you come to S
tephan's thread.
I hope I could help you.
Matz