Eric at OJ is great but I would give the guys a call at Acme. That X-80 would love one of their new 15" props. A 15x15.75 or 15x17.75 would work very well or they will have better suggestions. Plus they have more cup sizes to try.
Acme Props - 1-888-661-Acme
I just tried one of their 15" props and it is outstanding.
2008 X-45 Pro Tour Red and White