The line has an eye splice, and then a shackle, which goes through a hole near the trailing edge of the centerboard. I bought the line/shackle from Rudy at D&R Marine.
DR Marine Product Detail
It sounds like you need a much longer line than I do though. I looked quickly on Rudy's website, and he doesn't have an Oday 30 centerboard pennant pre-made. However, I bet if you give him a call, he can tell you exactly what you need. In case you didn't know, Rudy worked for Oday for many years, and now owns the molds to some of the boats and their components. Rudy is quite the Oday guru.
Thanks for all the info.
And yes, I did talk to Rudy in the past and he is certainly a great help for O'Day owners!
O'Day 30 - Stuart, FL
Oceanis 411 - South of France