I offered this:
When a block is found, send the winning nonce to other large miners and see if one doesn't return it.
* Apparently this can be difficult to do with Stratum.
* If you wait before broadcasting the winning block, another pool may publish first.
* If you publish the block and verify the suspected miner at the same time, the suspected miner may well see the published block and be able to falsely pass your test.
grnbrg.