Just happened to find some relevant material which should probably scale to
25 Amps.

     trace width         1mm       2.5mm
35 micron copper         3.0A      6.0A
70 micron copper         5.0A      10.0A

where a 20C temp rise is presumed acceptable - looks like about 2 oz copper
in a 7mm strip should handle 25 A though the table came with a note that
for high current, round wire is preferred.

From "Comparison of Flexible Circuits to Traditional Round Wire Harness in
Automotive Applications", S. Sheehan, M. Rider, IPC 5th Flex conference JUn
9-10 1999, supplement, page 1.

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