Not sure how it actually worked out, but I shipped my 14 ft Avon from Davis, CA to Easthampton, MA for $100 by UPS. I took the thwarts out, rolled it to fit in an old fridge box and took it to a local UPS store.
I was expecting more, but after measuring and weighing, they told me it would be $100. So, it might be worth throwing it in a box and taking it to the store to see what happens, each time I looked online I was seeing something in the neighborhood of $300.
Sounds like your shipping a kayak based on the GH length restrictions you talked about, I'm pretty sure that changes things from a weight restriction to a length restriction. For that I would suggest going to your local paddle shop and see how they ship boats. If you can get it shipped from the local paddle shop in Auburn you might be able to get the commercial shipping price which can be better.