Just torque the nut correctly. "Lock" washers are useless and don't actually prevent loosening of the fastener. They don't "lock" anything. They're designed to be a hardened bearing surface and compensate for developed looseness between components. This is coming from the ASME and NASA publications, not some rando opinion.
If you need to prevent BP fasteners from loosening, either torque it correctly, use the appropriate thread locking compound (think Loctite), or use mechanical fasteners designed to prevent loosening (think nylon insert nuts). And not that it really matters for plate usage, but nylon insert nuts are only rated for initial application. As soon as you loosen it, you're not guaranteed the same rating even if you were to exactly replicate torque values.
If you need to prevent BP fasteners from loosening, either torque it correctly, use the appropriate thread locking compound (think Loctite), or use mechanical fasteners designed to prevent loosening (think nylon insert nuts). And not that it really matters for plate usage, but nylon insert nuts are only rated for initial application. As soon as you loosen it, you're not guaranteed the same rating even if you were to exactly replicate torque values.
