On Mon, 01 Oct 2007 12:10:57 -0400, The Other Mike
wrote:

If so, how do you make sure
they don't fall off while the thinset is drying?

Not an expert here, but I recently watched a crew install cultured
stone (faux) on a large entryway for new home. They even placed the
stone on the ceiling. I just had to asked how they made the stone
stick to the ceiling. He explained to me that they mix the
mortar/thinset on the dry side with less water. He also stated that
they added lime to the mix (aids adhesion?).

Only a few fell off while setting. One right on his head

--
Oren

"The voices in my head may not be real, but they have some good ideas!"