John;
I use small insulated boxs from Superior Enterprises (their websight is on KS I think) but my shipping costs are over $35, more like $50.
Basically, fed ex wants you to have a box with at least a double container inside. I usually use a deli cup(s) which I than put in a bag then put the bagged cup into a plastic margarine tub or a coffee can so there is no way short of an air disaster anything is getting out.
I get lots of packages where the animals are only marginally contained, usually in just a cup. It isnt that much harder to pack them in a safe manner to eliminate any chance of escaped critters shutting down this avenue of shipping.
Fed Ex also requires that the box be labeled "live harmless reptiles" and the species and number being shipped. I just print a label with all of the info on it and glue it to the box.
hope this is some help...you might be able to shave some size off of the box but I would rather have a bit of bulk there for insulation and air space.
Peter
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Peter and Sara
Beouf River Reptiles