Regarding the vertical tail discussion, Ben I think you have a valid point that people just changed several things, and did not really change only one thing at a time as good engineering doctrine would dictate. (measure, change one variable, measure again, etc)

That being said, a slanted rudder hinge absolutely does have a positive up elevator effect, whether in knife edge, or spin entry. The Perigee I finished this last fall shows that tendency dramatically as I fly it. Compared to standards of the late 70's to early 80's, the Perigee tail shows a definite lack of area, and should be increased by at least 50%.

Compared to today's standards, the tail should be at least 50% larger, but also the body side area increased by a significant amount, along with a rudder hinge line that is vertical or nearly so.

Different times, different rules, both dictate different designs. It is fascinating to look at the evolution.