ValidusVentus

I see no reason to not use the JIS screws you have selected from McMaster-Carr as long as the flange heads fit. Just cut them to size as suggested. Its pretty hard to mess it up honestly.
When installing, just make sure the male and female threads are clean, as well as the bottom of screw head and its mating surface on the caliper so that the amount of preload on the fastener is consistent with the torque value you decide on.

Edit: With the larger flange heads, this will cause a slightly higher percentage of the tightening torque to be used in overcoming the friction under the flange head so to achieve the same amount of preload as oem you would probably tighten them to a slightly higher torque value.

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