Dear Brian,
Below is the feedback from NFC expert team:
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Customer can follow Antenna design guide with help of attached excel files and NXP NFC Design tool (select NTAG 5 product from drop-down menu). You can also use https://community.nxp.com/docs/DOC-341105
Gerber files are in the works to be uploaded to nxp.com.
Hopefully this will suffice customer's needs.
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Hope above information is helpful to you!
Have a nice day!
B.R,
Weidong