I think I have the perfect solution for mounting you rod holders on your Willie boat. I posted a question about a week ago, asking advice on whether to purchase a Willie or Clackacraft. I ended up buying the Willie from South River Marine (800)952-5330.
The salesman, Dave Traen sold me 3 rod holder mounts that require no drilling & are easily moved. They only fit a Willie with gunwale guard. I first saw them on a guide named Jerry Toman's Willie when we fished with him on the Clackamas River this spring. They mount to the Uni-rail and can be moved any time. They cost about $21.00 each. Hope this helps.
Troy