You have to remember that you will have a slightly less efficient engine as a twin over the same size single. I believe PAW makes a 60 so I would arm myself with at least the biggest they recommend for that engine and a tach and you will have to decide if it too much or too little a prop. It will probably take some trial and error and many props because you have a different dynamic for the engine and it will have a different red line rpm than a single.