I have now adjusted vardiff to push up more agressively than down, that should help with this.
It doesn't help. We need ~0.2 diff
Maybe use string in password to force higher diff?
What kind of hashrate is 0.2 optimal for? For ~22Mhs vardiff now settles at about 0.14 and this means 4 shares/min, anything above is probably prone to generating quite a few stales.