Try Mike Griffith at Oxford Aviation's ground school.
There have been many debates on this subject in Prune over the years , as a search will show. I only wish my late mate Chris Braund had got his flat plate Do28 into the air. Chris also claimed to have invented winglets when he flew a Seafire with the tips turned up, and achieved a 10 knot reduction in Vs.
Look for Oxford at
http://ask.oxfordaviation.net/viewforum and make a post there.