In short, how do you do this?

It is a very useful tool to be able to write rhythms across barlines; however, I have not been able to find a way to do this with tuplets. Since Mr. Casella apparently has figured out how (or at least make it look like it) in Green Beats 2009 (the Fumeiyo-Yori-Shi-Wo excerpt), I thought here would be a good place to ask.

Thanks!

It's in the Sibelius documentation. But the essence is that you create a time signature that is twice the counts of the one you are using (4/4 becomes 8/4). Write two bars as you would but within the time frame of that larger one. You then create a barline and do some hiding of the ";new"; time signature. The documentation is a lot more detailed than this, of course.

That makes so much sense! Although it seems like a jerry rig type of operation, it also seems to be very easy.