Is there a way to download the User Hash Rate data that's used to generate the Charts?
Currently, no, but if you only need daily data points you can download the CSV from your Rewards page.
I'm seeing about 1.7% stale shares with Antminer L3+. Ping time to us, us2, and generic addresses are around 28 ms, 66 ms, and 98 ms, respectively: [...]
I recently upgraded my cable modem and upgraded from CAT 5/6 to CAT 8 cabling and reduced the number of internal switches in the path from the miners to the modem. So now I'm at a loss as to how to further reduce the stale shares. Any suggestions?
I would guess that the two most likely possibilities are that the bulk of the latency arises either at the miner's level, before shares are actually sent over the network (which could happen because of a hardware or firmware issue or quirk), or at some point along the network path (e.g. by a firewall examining TCP traffic, which wouldn't affect ping times).