http://www.willswing.com/blogs/PilotBlogs/tabid/38/EntryId/307/-Thicker-is-better.aspx

I believe that Bill Soderquist was flying a Moyes glider and of course, he was
doing aerobatics. As I recall he hadn't replaced his wires in a while. He wrote:

I had thought just before launch that these wires are looking a
little bad and reminded my self to keep the speeds down as to better handle the
loads.

I'm not clear on what glider Dave Sheilds was flying.

Section 7A (The CIVL Sporting Code) states:

12. 3.1 Structural Cables

Minimum diameter of any structural external wire cables is 1.9 mm or 5/64
inches.

The earlier reports, pictures and discussion of the accidents last
year here. Some additional pictures
here.