[Zope] Distribution Tab for a ZClass Product

When I use the Distribution tab for a ZClass-based Product, I can select the objects that are in the Product and create the archive, but when I install it in a fresh Zope, the object is not on the "Add" list. The product.dat file is 16K, so it seems like something is in there. I wanted to use the standard distribution archive format because then people could install it using the same process they would any other Product. Right now, they have to explicitly import the Product from the Control Panel. (The advantage to that setup is that they get all of the source). Is there anything else I need to know about the Distribution tab? Thanks, Kevin