I probably have something I could send you for $25 S&H. email me if you are interested. [email protected]
It would be something in the .60-.75 range. While the .46 would fly your Cub just fine. I feel like you are going to have CG issue with that small engine. A Cub has a really short nose and you will have to add lead to get it right with a .46. IMHO.

David