Shipping LN2 dewars

[J.W. Pflugrath]

When shipping LN2 frozen crystals in a "dry" transport dewar...

Is it better send crystals frozen into solid freon or propane popsicles
   or just in held in LN2?

If held in LN2, did you get any frost or ice on the crystals?  Did the LN2
in the cryovials evaporate by the time the dewar was received?

Do you really pour off the liquid nitrogen, or ship with liquid still in 
the dewar?

What problems did you have and how did you overcome them?

Any anecdotes and opinions are welcome, but I'll also accept facts backed
up by rigorous scientific experimentation.

If you send replies directly to me, I'll post a summary

Thanks!

Jim <jwp at msc.com>