Palau does indeed collect a general
import duty, 3%. Genuine Yachts-in-Transit are exempt from
import fees on ANY item(s) no matter the value. This includes personal items as well as obvious expensive
new boat hardware. However they do want to know what you have, a local agent can help you clear your container items. It's quite likely you will be required by Customs to employ a local clearing agent. The agent will advise if you can group items like kitchen items, used or mechanics tools, used, rather than individual listing. A specific uniform product code is required for each line item, your agent can handle this. Well worth their fee!
Alternatively Palau has a US domestic post office, 96940. Flat rate Priority boxes arrive by the 100s, Amazon is quite popular here. Sending here via USPS there are two options "General Delivery" or to a specific pobox number. Both need the notation Yacht-in-Transit in the address. Join the RBYC, they have a dedicated box number and they will collect and hold your mail.