Let me start by saying I'm not a Bitcoin miner, but can't you increase the time period over which you calculate the hashrate?
We are developing a mining pool, and it would be beneficial for us to know the hashrate statistics of each worker over a 10-minute period to distribute rewards fairly. Essentially, we need the hashrate displayed by the miner's device to match the hashrate we calculate based on the difficulty of the shares (hashes) it submits.