iMac 27" Mid 2011 external monitor GPU (ODD) Fan control

I recently installed an SSD into my iMac and downloaded "Macs Fan Control" which works perfectly fine. However, when I plug in my external monitor via Thunderbolt, the GPU temperature increases for 10°C (50°F) to about 55°C (131°F) or something which I think is normal. Due to the temperature increase, the RPM of the ODD fan (which I use to cool the GPU) also increase to a hearable amount. (about 2000 RPM) I use following settings for the ODD cooler: - Sensor based value from GPU Diode - Temperature that fan speed will start to increase from: 45°C (113°F) - Maximum temperature: 70°C (158°F) Can or should I tweak my settings (increasing the temperature that fan speed will start to increase) without the risk of damaging the GPU?