Yes, you can indeed ship multiple very small frags in one bag, I have done it many many time safely. Here's how. Providing the frags are very small, I mean on a less than 1" x 1" chip of rock. Using a 4" x 8" bag, with the water level at least 3" to 4" above the frags with adaquate air above the water line, you can ship up to 3 very small frags in this bag. Take 2 small sandwich bags or ziplock baggies, the small ones, and scrunch them up and place them in the water. Then place up to 3 frags on opposite sides of the baggies which will serve as a cushion in transit for the frags. I would never do this with frags on rocks any larger than small chips of rock. Never, never frag the day before or the day of shipping. It only adds undue stress to your corals which will already become stressed from the shipping process. Again, back in my heavy frag selling days, I did this countless times with 100% success.
Mucho Reef