Looks like fixed fan speed works OK now. I'm using 48% for both cards.

I'm trying to make the miner auto switch to the most profitable coin among X11/X13/X15 algos, but nothing really works as intended. First I tried to use TMBSwitcher 1.01 but miner idles for more than 1h waiting for work from pool sometimes. I tried using 4010/4011 ports and somehow miner quit after some time. Now I'm trying with 4440/5550/6660 but miner just runs X11 algo when X15 is most profitable and don't know how to make it autoswitch to X15 (bullus' config had default X11 kernel but I deleted that string from config).