I have found that fish stay frozen as long as 20 hrs with no thawing if packed in waxed cardboard with a styrofoam inner liner. They cost about $15 for a 75lb box $18 for a 100lb and they are sold just about everywhere in Soldotna, they also come in smaller sizes. Be sure to pack boxes full, this will also help things to stay frozen longer. The airlines like these boxes because they pack better in the cargo hold. Check your airline for baggage amount and weight restrictions. Also take a permanite marker and duct tape with you.

The lodge I work for in SE AK also runs a fish prosessing plant that packages catches for fishermen from all over the world, and this method had never had any complaints about thawing.

I've been to Soldotna area several times and have lots of contacts for fishing if you have any questions send me an E-mail.

I hope this helps, have a great trip and catch lots of fish.