Not sure you would have a lot of luck with leaf cuttings for tuberous. Your better bet is a log cutting (a piece of stem with a node and a leaf attached at this node). Check out the Scottish web site for doing this kind of propagation.

http://www.scottishbegoniasociety.co.uk/13.html

http://www.scottishbegoniasociety.co.uk/resources/Is+leaves+the+answer.No2.pdf

Let us know how it works for you if you decide to try it!

I did something like this in the fall. living in zone 5 requires me to bring in my tubers during the winter. So I cut off leaves from these plants. Anyway, many rooted and some gave new little plants like explained in your link above. But I am wondering what to do now. It is April and they are rooted but some of the plants are still small. That article didn't say how to use the cuttings after they had rooted or what to do with the shoots! Do you have any advice or know of any other articles? Your link expected everybody to know what to do next, but I am a beginner!!