Using

`zcash/src/zcash-cli getnetworkhashps`

returns 2,255,317 H/s (Sol/s?) while difficulty is 41,438. So network Sol/s seems to be 54.4 x difficulty.

So 4,000 Sol/s has a 50% chance of getting a block today. Maybe someone with 50 GPUs at 100 Sol/s can confirm they've only gotten 1 bock.