Please be advised that the import taxes in Guatemala range from 0 to 15%. Also, if there is no invoice in the box, or the amount seems not right to the customs "experts", the law states "in dubio pro fiscus", allowing customs 1) to make up a value for the goods, and 2) decide the use of the goods, which will affect the import tax. To this amount, you must add 12% value added tax, plus shipping.

As for "Vessels in Transit", although Guatemla is a subscriber to the convention, it will take you more time and money to make use of this fact, than the actual cost of taxes. Feel free to make your own experiences!