Regarding dry ice shipping to GSC - would the samples not lose viability without any cryoprotectants?
Yes. Do what the company tells you. Ship on water ice by the fastest courier you can get. Synchronize your sampling time with courier deadlines to minimize time on ice. Also,
* Make sure the ice you place the sample in is already melting so that it is at 0 degC. This is best done by bagging ice cubes that have been floating in water rather than taking ice directly out of a freezer. If you use ice directly from the freezer, it will be below 0 degC, and it will freeze your sample.
* DO NOT directly expose your sample to any water or ice. The absence of salts in ordinary water will cause cells to explode. Bag your sample. Double bag the ice, and surround your sample with it. And then make sure the whole thing is inside some kind of spill-proof container. GSC may have a kit for doing all this.
To answer Justin's question, one reason that cryonics organizations that accept tissue samples might not use cryoprotectant is to avoid any pretense of viable preservation (as opposed to simple DNA preservation).