Have you tried control fan speed using any other software, e.g. Asus gpu tweak II?
Command -tt -50 should keep fans at 50% but that GPU has a thing they called 0dB technology and it starts fans at 55°C and stops them when temperature drops below that value.
Maybe you should try -tt -30 to keep fans at 30%, that way GPU should be above 55°C and fans would be spinning constantly.
I don't think that's right. -tt should be target temp, right? As in, the miner will adjust the fans to keep the temp at the -tt value. The args to do what you're suggesting should be -fanmin 30. Or am I an idiot?