Applesingle encode carbinized applications?

Hi.

I'm working on a new installer package for Mac, and I have a carbonized
application that I want to include.  How do I encode it as applesingle? 
Previously I've used Stuffit, but any version I've got sees the application as
a folder structure.  I've also tried Fetch 4, which will encode files as
applesingle as it uploads a file, but it doesn't even *see* the file when I try
to select it for uploading.

TIA

Rob