See the following web page for a great idea:
http://jellostore.archway.com/cgi-bin/cornerstore.storefront/3ff0509306f76630271...We have used one of these before and it works great. Just make the jello a bit thick and it does not leak!
If that works, then cement should work even better. Just spray the inside of the mold with Pam or some such, close it and pour in the cement mix. At $3.50 plus shipping each, that's way cheaper than any mold I have found on the web and you get six stones at at time. This is easier than the tennis ball method also
Yeah, I know they are egg shaped, but surely that won't matter all that much. Just always load them the same way in the pouch and you will know how to adjust for thier particular way of flight.
This is on my list for warmer weather when the cement will set up right.
Jeff <><