So this is my dual Eth/Sia config.
EthDcrMiner64.exe -epool us1.ethermine.org:4444 -ewal 0x70c06E09AE5A2b8ECa5863C68b725adadCefF5cb.worker1 -epsw x -dpool
http://sia-us-east1.nanopool.org:9980/miner/header?address=a124a4d27961737e104e67551298844133ddbc0444b1cd585aa8243dfed1c4f8355ba6fc166e -dcoin sia
I'm getting about 20MH/s Eth and 300MH/s Sia with a light overclock on an R9 285, and same rates on an R9 380. So exactly the same as my Decred hashrates on both.
One problem, though... Every few seconds when dual mining eth/sia, my system locks up, and it seems worse when anything visual happens. I'll turn off aero to see if it helps at all, so we'll see... Anyone else have that issue?
EDIT: Disabling aero seemed to do the trick, though I haven't tried streaming video or anything, which I was able to do quite well while mining Eth/Decred... Anyway, Thanks claymore for another awesome addition to your already incredible dual miner.